Zero Gear Catch-All.
Remember Wacky Wheels? Well this is pretty much Wacky Wheels mixed with a healthy dose of Mario Kart. Parallax and I gave it a shot this evening and it's pretty decent fun. It's free to play until sunday (you should see it at the bottom of your Steam list). If you see me on fire me an invite!
From the developer forums it looks like if this game gains a following they are interested in adding free maps and more karts/items.
Developer Website: http://myzerogear.com/about.htm