I'm using a high-def Sony HDR-DC9 camcorder for video. It does a great job for the in-car video if I remember to turn off auto-focus. It records to DV tape and is limited to 1 hour, but that works for me. I prefer the least compression possible, plus tape is cheap and I can either keep them to archive the original video or just reuse them. Anyway, soon after the tape is done the camera turns itself off so with the big battery I have in it will last all day. The tape loads from the top so I can swap in a new one in, turn the camera on, and start recording again, about 20 seconds during a pit stop.
For audio I tape stereo lapel mics to either the rear of the car near the tail lights (Out of the wind and far enough apart to take advantage of the stereo effect. You can hear the car behind you and which side of the car they are on.) or in the engine bay.
For some events I'll also use my older SD Sony camcorder as a VCR and the video source is a bullet cam mounted somewhere else on the car, looking back, or at the driver, or on top of the car, or for for track days I might put the bullet cam down low on the door looking past the front tires. The SD video makes for good picture-in-picture video in the high-def videos.
For stills I'm using a Nikon D70 with the 135 mm lens that cam with it. I'm entertaining the thought of getting a longer lens but the Canon 7D is looking interesting since it also does video, so I'm holding off on buying more Nikon lenses.
Nice photos looking back at the other cars on the track. How do you trigger the shutter release, or whatever the equivalent on the digital cameras is? I've mounted my D70 in the car before and driven laps with the remote in my hand (its small) and I just click it whenever I'm not busy with the steering.