If you are building a bankroll from zero 888 all the way as you can be winning (generally small) $$$ very quickly and they have a lot of daily freerolls.
partypoker if you have more patience. You will win tournament tickets, then may win $$$ in those tournaments.
Don't bother with pokerstars freerolls if you want to try and make some money quickly (structures mean you just have to get sooo lucky and you'll cash in so few)