Try
Pokerstars. They of course have real money games, but they also have hundreds of play money game tables that have no charge to use, of all different kinds. I was playing real money games on there for a while, but after losing too much money I just play free games there now and love it. They even have play money tournaments, and some of them get you a free entry into an actual real money tournament. In theory you could win one of them, go into the pay tournaments, and if you keep winning you could go all the way to the World Series of Poker without paying a cent. Both Chris Moneymaker and Greg Raymer, the last two World Series of Poker champions, got there from winning smaller Pokerstars sattelite tournaments. I can't recommend it more highly.