I found I won the Back-to-School Sweepstakes from Aspyr, one of the bigger Mac game publishers. This prize includes every one of their games and a fully-loaded MacBook Pro. And I very nearly missed it entirely because I skimmed over the first email they sent telling me I won.
So two lessons: 1, enter every sweepstakes you can find, because you might actually win, and 2, for the love of god, at least read part of the emails you get before deleting them.