Convictions (http://gedry.livejournal.com/225149.html) by Gedry is really good.

Summary: Dean makes a living in high class home invasion. Dean's careful, he never wanted anyone to get hurt. But when he discovers Castiel still at home while he and his team are robbing the house everything changes. Dean pays the price for his misdeeds but somehow, along the way, he manages to make a friend out of Castiel. A man still struggling with his own kind of incarceration. Their relationship offers Dean some comfort, but once he's done serving his time questions still remain. Are they friends, or something more? Can they make a life together out of the ashes of their old ones, or are they both still serving their sentences?