AK's thread is a good one.
I've got one too. You can pretty much mount it anywhere you can think. Watch out if you mount on your the upper portion of your windshield and in case it rains...obviously (after it happened to me) it will interfere with your wipers. For inside shots, I mounted on the rear hatch window. In AK's thread, he has mounted at the bottom of the rear bumper to show the under side of the car, which is cool.
There's a lot of wind noise at speed, but I placed a thin piece of foam between the camera and door of the case, and that reduced it slightly...wind noise is still there though. Here's a sample with the camera attached to the passenger side B pillar:
YouTube - ‪370Z Stratotech Time Attack 4 - Aug 30, 2010‬‏
You see these everywhere in drifting, car racing, sports, etc. Have fun with your GoPro.