You have to go to PokerStars.com for real money. You can also try on of the subscription sites. It pays real money also.
You can play poker legally on http://www.spadeclub.com
. It is sponsored by cardplayer magazine and if you use the code ACESFULL you can get a two week free trial. It pays real cash prizes when you win. They base it on sweepstakes laws.
You can also play blackjack and poker at http://www.clububt.com
, it will show you the prizes that you can play for. It does cost $20 month to join. If you register and enter this code WEC97XUK, it will give you two free weeks on their site. I have a paid membership there and I've won real cash there and they do pay.
Both sites are legal to play at in the USA.