The following poker sites are U.S. friendly, and you can play either for free or for money:

6/30/08 - Pure Play Poker
Grand (1): Win a seat at the Main Event in the World Series of Poker or $10,000 cash alternative. Daily and weekly cash tournaments available, too. Age 18+ or age of majority. Open in US. Void in PR.

AbsolutePoker.com
Get a 100% first time deposit bonus for up to $750!

Doyle's Room
This is the home of the master Doyle Brunson.

Full Tilt Poker
Play for free or for money. Free 100% bonus up to $600! This is where we play -- Join us sometime at the low-money ring games. Username: kb1gig

Party Poker
One of the most popular poker sites on the Web. Play for free. There are always games starting whenever you sign in. Get 20% free up to $100!