If you just start playing go to pokerstrategy.org.uk and sign up for a party poker account over that site. you get 50$ for free plus another 100 for playing a little. You only need to do some reading (but thats a good idea no matter where you start or this whole game can get very expensive) and finish some kind of quiz.
That's a great way to start playing poker wioth out risking any of your own money.
Other than that I play on pacific poker (easy competition, but that graphics are horrible), interpoker (pretty tough, but GREAT bonus system and rakeback. Also most games are short handed, which is not a good place to start for a beginner) and bwin (pokerroom skin, easy competition, no bonus, horrible software
)
I also still have some money on poker stars, but i didnt play there in the last few month because its pretty hard to make any money from all these rocks :/)