Well, playing poker online in the US is kinda illegal. I don't think they are going to knock on your door and arrest you. They have made it illegal for banks and financial institutions to do business with online poker sites which are all based offshore. That just makes it a little troublesome to fund your online poker account. I had trouble using my checking account info to fund my account, butI used my ATM card which drew from the same account with no problem.
Online poker is only illegal in some states. Stick with the sites that have the most players poker stars, Full tilt, Titan, etc...There might be some laws in place in the future to deem poker as a game of skill and having it fully legalized.