I am also in the USA, so I have the same limitations. America's Cardroom is nice, I probably play there more than any other site. You can also play at intertops and BetOnline. ACR and Intertops have some regular freerolls if you are looking for that. If you do sign up for the sites, it would be nice if you clicked through a CardsChat link from the forum.
I play on pokerstars for play money in the league and in CardsChat events. I like this site a lot and I wish I could play for real money on this one.
I currently play mostly on Bovada which is unique with it's anonymous format and from what I can tell the biggest/most frequent "guarantees" with tournies for US players who don't have Pokerstars or 888 in their state) , and also recently been playing more on BetOnline.
Bovada is pretty soft and nice set up. BetOnline seems insanely soft but super swingy. Neither offer rakeback but do offer "points" you can redeem for tourney tix. Neither offer much SNG traffic but then again SNGs seem like a dying format anyways (outside of Spin n Gos and Jackpot games).
Tournaments, Breakout and GG are good for playing a solid poker (freerolls in my opinion of the best) the rivals fold you and you do not face so much variance, partypoker has a Cardmate at 11 am and starts with 100k blind chips 500/1000 if that's deep because I have to admit that I feel very comfortable with that kind of tournaments, for cash zoom, 888poker and PokerStars simply because of the number of players in the room. I should give focus to ACR you can take money without first deposit but I do not finish hooking.
It depends on what suits your needs, if you are regular cash you should try on titan or party if rake. The rest I always recommend is PokerStars and 888Poker