888 Poker may reenter the US market very soon. Experts expect this to happen sometime in 2015. 888 Poker left the USA market back in 2006 when the UIGEA was passed in the congress.
Update 2014: Players from New Jersey (NJ) can legally play on 888 Poker. This means that they can deposit and withdraw using many payment methods, without problems. Due to this fact, together with Party Poker, they have earn the trust of the congress and both parties are in discussion currently. More states are expected to enter the legal poker market soon. 888 Poker is one of the first poker sites to get a New Jersey License.
Read the 888 poker bonus page. All US players can register a play money account now, this way you will get an email from 888 poker once the accept real money play.