Replying to To the NS Lawyers

First off I'm in the U.S. and stupid responses will be ignored and no I'm not going to spark note it.

Here is the situation that I am currently at.  I spent a semester studying aboard in Shanghai.  While I was there my old roommate received our whole security deposit back from our landlord after our lease expired.  He went on to spend my share of it, $800.  I come back to the country and he goes and leaves the state and moves back to Maryland about 2 weeks after I get back.  I tried my best to get him to pay me before he left, he isn't the most reliable person.  

So I keep nagging him for the money and he tells me "Yea the check is in the mail." I believe him, bad on my part I know.  A week passes and no check, call him he says he sent it.  Another week, two weeks go by and I'm pissed.  I need this $800 for my security deposit at the place I'm living next year.  Keep calling, texting, emailing him about it, a couple more weeks go by.  He keeps saying he sent it.  I bring up the idea of him just paypal-ing me my money and he seems down for it.  Now he is ignoring me.  I have saved all the texts, emails, and messages between me and him just-in-case this happened.  I also have the invoice sent to me from my former landlord saying that the total deposit was paid to my roommate.

So my question to you, fellow NS, what legal actions can I take, if any???  I am a poor, working college student and $800 is a lot of money for me.  

Any help?
Thanks,
Piper