Prime Verse (http://archiveofourown.org/series/14309) by meus_venator: "In a cruel and capricious society where slavery is the norm, first born children or Primes become masters, all younger siblings become slaves or Secs at the age of sixteen. Second born son, Sam Winchester, has evaded his fate and helped others do the same while attending college and living as a Ghost, but his luck has just run out." (unrelated Sam/Dean)

The Child Corrupted (http://archiveofourown.org/works/523986) by lexicale: "Sam grew up in Master Azazel's house -- he doesn't know any different kind of world. When a hunter named Dean Winchester frees him, he doesn't even know that he's free. In his mind, he merely has a new master. Dean, of course, is oblivious." (Sam/Dean)

If you don't mind complete AUs, I really enjoyed The Winning Scenario (http://virtualpersonal.livejournal.com/241801.html) by virtualpersonal: "Disguised as a merchant during an information gathering mission on a gaming and pleasure station, Captain Dean hits the jackpot. Surprised to learn his winnings include a night with a pleasure slave, he is ready to reject the slave's services until he learns that the slave is human. There is no way he will leave one of his kind behind, no way. The pleasure slave, Sam, has his own secrets. Cylon torture and conditioning to make him a suitable commodity for the slave trade has left him with half memories, nightmares and psychological problems. If he knew Dean was a colonial warrior, there is no way he would leave with Dean and no way he would go anywhere near Dean's destination, the Battlestar Galactica." (unrelated Sam/Dean)

That's awesome! Really, I appreciate it. I have read a few of those, but most were new to me. I don't mind complete AUs at all. Thanks.