Just finished putting together some pieces for my "2.0" version in-car setup.
For my previous trackday at Thunderhill last weekend, I built a camera mount for the roof to get a good view of the car's line on the track. In-car footage doesn't let you really assess how close to curbs you're getting, but putting the camera on the roof does.
One thing I miss with the roof cam is the ability to see what's going on inside the car with the steering wheel, gauges, knees, and head. Short of getting a Picture-in-picture box, I decided to put the camera back inside the car.
With the lipstick camera, I have to keep the camcorder somewhere in the car other than my usual mount. With the roof-cam, I had it stuffed in the glove box, but I don't really like the safety aspect of the weak glove box latch. I had the idea last night to use the bolts that hold the seat down to attach a bracket. The bracket would then use the tripod mount on the camcorder to hold it close to the floor.
Another problem with in-car footage is that the camera doesn't know to expose for the car interior, thus washing out the bright exterior; or vice-versa. I saw that a couple fellow trackjunkies had attached sunglasses material to their cameras to shade the top half (where the windshield is in the image), to balance the image intensity. I was talking with my wife about this, and she suggested using window tint on the clear glass lens protector.
I made two versions of this, one with a single layer of tint, one with two layers. In my limited tests, the single layer seems to work well. I haven't tried the double layer yet.
Here is a video from inside the car at Thunderhill Raceway:
http://www.thenobot.org/video/video.thenobot.org/20060913-thill.mov.jpg More photos and descriptions of the setup are here.