I use this:
Made by these guys:
http://delkin.com/fat-gecko-camera-m...camera-mounts/
It works great! And has so many mounting options, works on almost any smooth hard surface, glass, metal, plastic, etc. I can be broken down into smaller/simpler parts, but using the whole thing its VERY stable. I can shake the car with it, and it is helps create virtually shake free videos even in the rough environment of RallyCross.