Three weeks ago a newsletter I subscribe to announced that PlayersOnly.com had a surprisingly good bonus offer. Deposit $200 on Wednesday, bet $200 on Wednesday, and you get a $200 bonus the next day. To collect the bonus, playthrough is 20x, or $4000.
So basically, deposit $200, get $200 more for free, and wager $4200. If you play blackjack, a 0.54% house edge game, you'll have an average loss to the house of $4200 x 0.0054, or $22.68, for an average net profit of $177.32. Even at $5 a hand, it goes fairly quickly.
The first week, I ended up $100; the second, $400 more.
PlayersOnly has the appearance of a fairly solid online casino. They've had glossy multi-page ads in Card Player and Poker News for several months now; they've gotten very little bad press on Casinomeister.com; and they have the recommendation of OBJ as one of the few sites that still take US players. I goofed on week 1 and deposited in their sister site, Sportsbook.com, and the withdrawal of a check for those funds arrived fairly quickly.
The only drawback -- any withdrawals after the first one each calendar month are assessed a $40 fee. Essentially, it's one withdrawal per month.