I heard about this one in Bitcointalk.
It's a Bitcoin based sportsbook.
Quite low limits e.g. in the NBA you can bet 0.111 BTC max once, then bet another 0.111 BTC again and 0.111 BTC again, in many other sports it's 0.037 BTC max (you can bet more, but the odds will drop, unless if you bet now and again with intervals of some hours, then the odds will probably adjust themselves).
The benefit? Instant Withdrawals.
Another benefit? Looks like US members can participate.
The site does mention only 1 account per person, but it only requires email + password.
I tested it for 0.56 BTC withdrawal, I did indeed receive it instantly upon submitting it, not even waiting 1 second, it sends withdrawals immediately.
Feel free to check it out.