http://www.hardforum.com/showthread.php?s=&threadid=432014
I havn't tried this yet, but supposively the jist is that if you work for a retailer that sells Xboxes and is participating in this Prize Shop thing (there's a big list), you can answer a bunch of quizzes to earn points. With these points you can earn free Xbox games and accessories, although you still have to pay about $8 in shipping..