I'm in the U.S., so I have to say Bovada. ACR is alright, but their software is kinda janky and I've had problems with disconnections / freezing during crucial points of tournaments last time I played there.
I can't help but cringe a bit every time someone says Pokerstars has a lot or good freerolls. I used to be a big fan of stars, now not so much. I'm primarily oriented towards Full Tilt, 888 and PartyPoker right now, with Full Tilt being my favorite by a longshot.