The US is currently going through a series of amendments which may end up enabling online gambling in many states, if not through a federal law which will allow interstate gambling throughout different areas in the country.
Still, payment acceptance regulations for casinos and banking systems may take some time, including federal financial changes. For solving this situation, Bitcoin, an experimental new digital currency, has been considered as a possible solution to ease up the way for regulated online gambling transactions in the US.
Bitcoin is a crypto-currency that enables instant payments by using P2P technology (similar to Bit Torrent) without a central bank or any government financial institution. Transactions are handled online through Bitcoin and carried out collectively by the network; and users’ demand quantifies the exchange rate at any time.
Even if it sounds like a hacker invention, Bitcoin is currently legal in the US. American companies like Wal-Mart and 7-Eleven stores are already accepting Bitcoin as an official payment method.
The crypto-currency is still under further development and enhancement, with legal aspects yet pending extra support from federal US financial institutions. According to one of the co-founders, Gavin Andresen, chief scientist for Bitcoin Foundation:

It’s still a pretty raw technology […] It’s pretty obvious that it’s been designed by geeks for geeks. It’s not easy to use yet, but it’s getting easier all the time.

The digital currency has become crucial for foreign companies accepting US customers, with some Canadian-based casinos like Infinity Poker, and Costa Rica’s Strike Sapphire, accepting Bitcoin currency from US players. If US legislations for online gambling get full approval, Bitcoin would probably be one of the main valid payment methods for casino sites.