I mentioned this last year and a couple other people seemed interested so I thought it would be a good idea to compile a list here of places/websites/companies/whatever that are doing any sort of bracket challenges. Of course there's the Billion Dollar Bracket on Yahoo!, so are we going to be using Yahoo! Sports this year again? If so I think that automatically enters you into that one.
I haven't seen any others yet, but there were some free ones last year with good prizes so as they pop up I'll add them to this thread. Anybody else?