There are various ways to play Texas Hold em online for free. Places such as Global Poker, PokerStars Play, and the World Series of Poker all offer free ways to play the game of holdem.
Real money online poker is legal and available in New Jersey, Pennsylvania, Nevada, Michigan and Delaware. It's also legal in Connecticut and West Virginia, but yet to go live there. The top NJ online casinos and Pennsylvania sites are the leaders in online poker.