If you're looking for access to Emini S&P a good futures broker is Cannon Trading. I've had a good experience with them. Of course do your due diligence. Nothing worse than blindly taking a suggestion.
http://www.openecry.com Check out a few demo's and see what you like. OEC has a great platform that includes data for live accounts.
Although they were a MAJOR pain in the ass to open an LLC account, AMP futures work well for me. I pay about $4.80 round turn. I'm sure this could be negotiated if you trade some size, I trade less than 10 lots/es so I don't think I have much negotiating power. I have an individual account with them also. Easy to open.
http://www.elitetrader.com/br/ Many scammers out there. Stick with those most reviewed, and with best reviews. Tom