I love Poker Champs the most: the cool/slick graphics, the professional style of play, five freerolls a day (no deposit), 10 at a table. I'm a sucker for turbos. Besides the site is owned by Gus Hansen, who often plays on the site, including freerolls sometimes just to say hi.
Poker Stars #2, though the amount of people who can get in a tourney can be daunting. The 54 seat playchip sit-n-gos are good practice when you're first starting out. They handle forum freerolls well.
Absolute Poker third. The freerolls there are respectable (and no deposit), though people play crazy early in the tourneys. They handle forums well.
Ultimate Bet a distant fourth. I hate their Pending Bonus Dollar program which seems like a gyp to me, but they're the best site to play Crazy Pineapple. I wish poker sites had more Hold'em variations, whether Irish Hold'em, Tahoe or Super 8.