I just plugged my monopoly money from BTC-Arbs into http://remitrade.com/?partner=sev09.  Feel free to use my referral or not.  I've only been in a few days, but it's paying out.  You can't withdraw your money until the end of the "investment period", though.  Enter at your own risk.

RemiTrade had good reviews from InstantScamAlert.com, though, so I thought I'd give it a shot.  It's play money, after all.