SweetwaterRC.com for some Carpet. Normally races are just 1/18th, but for their trophy event which is held at a larger venue they hosted 1/10th's as well.
I've never really seen asphalt off-road though. Here in Riverton, we run a gearbox class with is to get the off-road guys to run their cars on-road style and hopefully get them into the on-road classes.
www.wyomingrc.com | www.wyomingmodelerspark.com