ESPN Tournament Challenge
This is the biggest one of them all; millions of entries each year since each person can have up to ten. The prize is a $10,000 Best Buy Gift card, but it is awarded to a random entrant from the top 1% of scorers. It used to be fun watching the leaderboard, but that has lost it's luster with the random drawing.
CBS Sports Bracket Challenge
Similar to the ESPN game, CBS Sports is awarding a prize to a random entrant who scores in the top 10%. The prize is a $6,000 cash and four tickets to the 2013 Final Four. After you make your picks, watch all the games from your computer with March Madness On Demand. It's even more fun if you watch from your office.
Sporting News Bracket Insanity
This one is hosted through Facebook, so you you must authorize the app to play the game. This is a round-by-round game, so you have to make sure to make your picks in a timely manner. Because it's on Facebook, making groups and joining pools is a breeze. The prize is, well, nothing -- unless you charge an entry fee for your pool, which we would never endorse, of course.
Yahoo! Tourney Pick'em
This game offers the best prize package, awarding a prize for best overall bracket and a lottery-like loot for a perfect bracket (yeah right). The first overall prize is $10,000 Cash and is awarded to the best bracket. An additional prize of $5 Million Cash would be awarded to a perfect bracket, if that were even possible.