There's this new website called BetAgainstMe.com . Basically it is an ad supported FREE gambling site. What makes it legal is the fact that you are not betting with your own money.
You are given 20K of play-money to bet with every week. If you do it better than other players, you will win real cash prizes. The winners are decided based on the amount of play-money in their accounts. There are daily, weekly, and grand prizes. By inviting friends to the site, you receive additional 1k for placing bets and make 10% of what they win (if the do). Simply register at http://www.betagainstme.com/... to get started.
Check out this video they did to promote their site of a degenerate getting his finger cut off: