mt_mck7

If he's from your ward, some photos of ward/stake activities might be a good connection to home.  Maybe pass around a card at each activity for folks to sign and send it with the photos.
Really, even if he's not from there, they'd likely be appreciated.

And KD. Gotta have KD! (Kraft Dinner, mac and cheese)
And peanut butter!

@mt_mck7 - You could also do scripture quotes and/or hymn lyrics: 
"be strong and of a good courage"
"let your light so shine"
"hold to the rod"
"scatter sunshine"
"count your many blessings"
etc, etc, etc

"praying for you"
"you are awesome"
"so proud of you"
if he's in a foreign speaking mission - just say these (and what you have been) in that language (use google)
 

How about an envelope stuffed full of confetti? Very popular! I would send silly notes. Penguin jokes! Cheer him up!

I'm going to go against the majority here and side with LDM. Tell your friend that you were touched when he told you he liked you, and that you were too taken off-guard and embarrassed to tell him that you have liked him for a long time.
But after telling him that, I think it would be wise to tell him that you're very glad he's serving a mission, that's where he belongs, you support him in that, and you don't want to be any sort of distraction from that. So you're happy to see him until he leaves, but you think you both would be better off to keep things as "just friends" until after his mission is done. At that point, you'd love to date him seriously and explore other possibilities.
P.S. Even on the internet, my name is not Dear Abby or Ask Amy or any of those other awful Bad-Advice Columnists. But that doesn't mean my advice isn't bad...

I wish I had told my girlfriend (now wife) how deep my feelings for her were before I left.  Not telling was part of what lead to her making some unwise decisions and although it turned out OK in the end it easily could have resulted in something really bad for both of us.  How many times in some movie have things gone south for a couple because they are not honest with each other about how they feel?  Better to both have a grip on the reality of the situation than have somebody walking around with a mistaken ides of how things are.  If you feel you have to manipulate him by withholding information to get him to do the right thing what does that say?
So I say tell him, but also make it clear that his willingness to serve a mission is one of the things that makes him attractive to you.  You might even want to say that if he ever uses you as an excuse to bail out or slack off it will make you reconsider your feelings for him if you are worried about that.  A girlfriend can be a great source of strength and support to a missionary if she plays her cards right.
See also the list of things I posted in this tread:
 

So, there's these neuro drinks that have a bunch of different flavors. There's the sonic (that gives you energy), bliss, and I think sleep is one of them too. I've had them every so often, and I usually have the sonics because that gives me more energy and I'm able to be more focused. I don't have them everyday, but I just got one of them from the grocery store this morning, and it wasn't until now that I looked at the ingredients. One of the ingredients it L-Theanine (L-TeaActive), so I looked it up. It said that L-Theanine is an ingredient in tea that comes from the tea-leaf, and I was wondering that since that's in it, it might be against the word of wisdom (the word of wisdom is where members of the LDS church are encouraged not to drink tea, coffee, beer, or anything that can take away our free agency). Are the Neuro drinks against the word of wisdom?

You dont say if he knows you, if you have some relationship with him etc..you said you speak with his parents so I assume you know each other.

That being said, I dont know him but if some young lady were writing me and I was interested in her my priority would be to write her back before anyone else to include my parents. That is just me though. Most kids these days find it an ordeal to even put pen to paper much less address an envelope and go through the hardship of just enduring the letter writing effort. So either he is just isnt into you, he is lazy and inconsiderate or he just has not received your letter(s) yet. Your guess is as good as mine.

Many will make excuses that since he is in the MTC/on mission that he has little or no time. Until I see an MTC schedule that remotely resembles Army or USMC boot camp then he has time enough to write a novel to you.I didnt go on a mission, but I have been in many conversations over the years where RMs discussed how rough the MTC was in terms of lack of sleep. Ill just say this- it aint that tough if what they say is true.

If I (and everyone else) could write multiple letters home and to my GF each week while I was in boot camp then someone at the MTC can write too- they are just choosing not to.

If my daughter were writing a missionary and he never wrote back Id tell her to dump him. If you are not worth writing to in his mind then he is not worth being around.

We had a missionary from our ward who recently came home from his mission.  We've been writing to him for 2 years without a single reply back.  He did send letters to his mom every week where he would sometimes express gratitude for everybody who wrote him letters and how it has kept his spirits up and how it kept him feeling that he still has a strong connection with his ward family.

I'd say just leave it for now, but if he asks to take you out again or something I'd remind him of what he did before and you won't take kindly to him doing that again, and ask him if you can count on him this time before you accept.

Rule of thumb.  Effort + time reflect a lot about interest and intentions. Things come up, and sometimes plans do have to be cancelled, but someone should quickly make new plans and then follow through with them. If someone avoids, changes plans, and does not actively correct things, make new plans etc..... then you pretty much can see that they are not very interested or even respectful of you.  Its not really even worth addressing, if he is isn't interested it won't result in him changing his behaviors and going out with you. It likely just will create more awkardness for both of you, and needless additional heartache for you.

He is not playing games with you and he his not stringing you along...  He has already clearly stated his intention and is acting accordingly.
 
You might want more...  that is to bad because he isn't going to give it to you.  You need to focus your attention elsewhere...  Until you do you will be stringing yourself along.
 

One of the policies on this website is to explain doctrine that Non-LDS Members might not understand. I wrote it for both people who are members and aren't members.

Okay, this is a personality type mismatch.  You are both still learning your place in the world.  Still growing up.  But you are in a situation where you have a very strong personality interacting with a very mild personality.  The natural direction this relationship is going to go (if untamed) is that the strong personality will roll over the mild one until the mild one reaches a breaking point and either, breaks or pushes back.
I'm of a strong personality myself but I had parents who beat my butt - literally - to discipline me so I was able to mostly behave appropriately in public as I was growing up.
My sister is a mild personality and she was the baby in the family so she was "delicately handled" and so she never learned to assert herself so until today, when we discuss family issues and I want it solved one way and she wants it solved the other way, we would do it my way because she wouldn't say anything!  I would just find out that she did not like what we were doing because I would hear about it from someone about how she's crying or something... it gets so frustrating trying to figure out if what I want is okay with her.  And we've talked about it some and she said she doesn't want to say anything because she's afraid I would question her or challenge her about what she thinks is the right way and she hates my confrontational personality.
Anyway, when you have this kind of mismatch, BOTH of you need to realize you have to strike a balance.  Unfortunately, you can't control what somebody else does, you can only control yourself.  So, you will need to learn to be more assertive so you can check her impulses and provide the balance.  You can't just "suffer in silence" because she won't know she's stepped beyond her boundaries.  Anytime you start to feel uncomfortable practice saying this line, "I'm sorry, I'm uncomfortable with that.".  Say it with a smile.  When she starts to argue or push, "Listen politely (she might have a point), then if you're still not comfortable with it then repeat yourself - I'm sorry, I'm uncomfortable with that."  If you can offer an alternate activity that you're comfortable with then offer that as a negotiation.  But be firm about standing on a plain where you're comfortable.  Then she will learn where her boundaries are and you both can decide whether you can still be friends with the boundaries you set for yourselves.
You won't really know if you have any influence on a person until you try.
So, say you're driving and she controls the music and puts garbage on... turn it off and say, I'm not comfortable with that.  If she insists, stop the car on the side of the road, and say it again, I'm not comfortable with that.  Then offer to play something that you think she might like that is not garbage.  You're driving.  You have control of this situation as it is your car.  If you're not comfortable, nobody is going anywhere... so, next time she rides in your car, she'll know not to play garbage.
If you're riding in her car, you're not in a strong position of control.  It's her car.  But, you can still exert some control by telling her that you really don't like that garbage as it is against your personal convictions.  If you both value your friendship, you'll try to find some music you both can enjoy, or if you're just too different in this regard, then you can agree to turn off the radio and you can just talk.  If her strong personality has to insist on her music as it is her car, then you know to just take your car next time.
Hope this helps.

@askandanswer
You should never make someone's lack of interest in the Church the reason to terminate a relationship.  IMHO, the OP has plenty of good reasons without even bringing the Church into it.
 
My thoughts to the OP:
Tell her that it upsets you that she doesn't support you in your beliefs/standards.  Tell her that there have been many instances where you have felt used by her.  Then let her know that you refuse to hang out with her anymore.  Period.

This might sound like a slightly Machiavellian approach, so I don’t feel wholly comfortable with it, but I offer it here in the hope that it might be helpful.
I suggest you take the offensive – start asking things of her instead of her always asking stuff from you. Specifically, I suggest that you invite her to church. I suspect she will refuse. This refusal then becomes the basis for the termination of the “friendship.” You could explain to her how important church is to you and how your character/values/identity have all been significantly influenced by your beliefs and church membership and that because your church membership means so much to you, and is such an important part of your life, you would like her to have the opportunity to experience the blessings of church membership. If she is not interested in a) learning more about what has made you the person that you are, a person who she claims to like and be friends with, and b) exposing herself to an opportunity that could help to strengthen her moral values and character, then I think you can use her refusal as a legitimate reason to terminate the relationship. If she’s not interested in learning more about why you are who you are, then her interest in you seems to be somewhat shallow, and her refusal to come to church should be a clear demonstration of how shallow her interest is, both  to you, and to herself.
Of course, if she does come to church, and comes on a regular basis, that provides a great opportunity for you and her to start helping her shift her values, priorities and behaviours more towards those that you would feel more comfortable with.

You don't need her.  Make your boundaries clear to her and make it clear that if she wants to continue the friendship she has to respect those boundaries.  If she doesn't want to do that, or says she will but keeps violating them, you end it.  If you dont' do that, then she won't take your standards seriously or respect them.

Most of the backstory was in another post where she was unsure about what to do with her feelings for this guy, but the dream part is new.

At this point, other than it meaning you have feelings for him and miss him I don't think anybody here can read anything more into your dream than that.  If it isn't a dream that knocks you up the side of the head as an obvious revelation, or if praying to understand it doesn't help then you just have to file it away for future reference and let time show if it meant anything more.  Write it in your journal and go back to it in a couple of years.
I do hope that you and this guy have talked about things.  Don't leave this needlessly ambiguous.  There is nothing wrong with starting a relationship now as long as you both have the mission set as the priority.  If he returns your feelings (and you need to ask him about that, don't assume based on what you describe) then you need to be on the same page for how you are going to deal with the mission.  Do you consider yourself waiting for him, does he want you to wait for him, what does 'waiting' mean to each of you?  Is he OK with you dating others while he is away to see if you can find somebody better?  Is he OK with you having a romance with somebody else while he is away, or would he want you to Dear John him before getting into a romance with another guy?  What are the limits?  Would he feel it would be disloyal f you held hands with another guy?  Kissed another guy? Told another guy you were in love with them. A lack of clarity on these things can cause either one of you a lot of needless emotional pain.

For starters, I'd like to congratulate you on standing up for yourself realizing what is and is not good for you.  There are many red flags about this "friendship" and it is not okay.
What you're going to have to do is tell her "no" and keep telling her "no".  I'm guessing that she's not used to hearing that, and will beg/threaten/apologize over and over again until she's can keep using you as a door mat again.  Be prepared for that, and keep telling her "no".  If she's unwilling to treat you as the Daughter of God that you ARE then she is no friend.
 
(Also-- it is illegal for her to drive your car, because she is not specifically (aka by name) covered under your insurance.   If she gets pulled over or in an accident it'll be a nightmare for the both of you).  

Just because a guy has a girlfriend while on his mission doesn't mean that he isn't going to be as good of a missionary or that his girl will be a hindrance.  It depends on how he chooses to treat the situation and how she chooses to act as well.  I met my future wife when I was 17 and I knew the night we met that she was the one.  Two years later to the day I was set apart as a missionary.  She never once did anything to try and discourage me from serving a mission, in fact she was very encouraging and told me that first night that really like guys who were planning to serve a mission.  I didn't need her encouragement, serving a mission was something I wanted to do since I was quite young, but the fact that she encourage me to go was something that made me respect and love her more.
She didn't write me letters that distracted me from the work, and I was motivated to be a missionary that she would be proud of.  There were hard times where her kind words really helped, and often she was the only one I could pour out my heart to. I didn't wish I was back with her, I wished she could be there sharing my mission.
I don't know your or your or your guy so I can't say if it would be like that for you, you have to make that call yourself based on your knowledge of him and on prayer.  You can tell him you have feelings for him and that it's very important to you that you don't interfere with his mission, ask him how he thinks the two of you should handle it.  It concerns him too. 
Whatever the case, write to him and keep that connection alive whether it is as a friend or as a girlfriend.  And while he is away, keep your eyes open.  Use him as a standard to measure other guys against as you get to know them.  If you can't find somebody better them him over the next two years then he wins a chance to continue and expand his relationship with you and you have the security of knowing you have someone lined up for later so there is no pressure to get into a relationship with somebody else now.  You can be picky, you can wait. 
If this becomes a case of you are his girlfriend and waiting for him, you both need to be clear and agree on just what that means.  Make sure you know what kind of relationships with other guys he would be OK with and what he would feel was being disloyal.  At what point would a Dear John letter be appropriate?  I've seen some girls think that anything is fine and they would only Dear John a missionary if they got engaged.  And I've known guys that felt deeply betrayed over their girlfriend sharing a kiss with another guy.  You need to be on the same page if you go there.