I know that after "Black Friday" many online poker sites didn't allow U.S. Players to play for real money anymore. I've heard/seen that it's possible to play via bitcoins and/or other proxy methods. Other than those ways described, is it possible to play in the US for real money?
As of July 2012, the two biggest places for US players to play are currently on sites that are part of either the Merge Network (such as Carbon Poker and Black Chip Poker) or the Revolution Gaming Network (such as Lock Poker and Cake Poker). Both sets of sites get a reasonable amount of traffic, offer good rewards and rakeback, and most importantly still accept US players. I deposited with one of them using my credit card in early July.
It's also worth noting that Nevada and Delaware have passed laws to license and regulate intrastate online poker by the end of 2012. That should create new options for players residing in those states, but it might also make it so those players can't play on foreign sites (which includes every site currently in operation).
I believe plenty of sites offer ways (I am sure PokerStars does ) to play for real money. The trick is you are never "playing for cash".
You purchase some "gaming currency" with real money, then you can gamble with the "gaming currency" and eventually cash out the gaming currency for USD.
edit(1): It appears it's much easier than I thought... Looks like it's as simple as throwing down a little plastic. Links below:
Edit(2): I stand corrected. http://www.pokerstars.com/usaplayers/faq/