Whaleclub has become pretty well-known over the past year in the bitcoin community. Allows you to trade FX and commodities with btc only and no verification.

Their fees are less than simplefx and UI/speed is better generally. I think simplefx converts your btc or basically bets against you or something like that. Ive tried both and am on whaleclub right now, has worked fine and have not had issues with them.