My buddy and I have started running ours on a new section of blacktop parking lot at work. We went and looked at it first to make sure it is flat and clean enough. A little advice though. First have hard tires on your car and second put hard springs on it. If you use soft tires they'll fly off on turns. The springs help by keeping the car from bouncing down and scraping up the under side. If you have one of the trucks then these won't be a concern.
I'm lucky here. One of my local Radioshack dealers has one of the foam XMod tracks set up in an oval. It's cool because they're technically not a Radioshack, but a dealer that sells Radioshack parts, so they have stuff that other Radioshacks don't. I also have a local slot car raceway where the guy is going to cover up one of his slot car tracks temporarily with a material and start having XMod races for people. It's gonna be awesome.