I believe the keith code school uses this lens: http://www.helmetcamera.com/index.htm the picture quality is decent, not as nice as the camera itself though. I do remember them saying they went through a few cameras before figuring out the sony dv's were the only ones up for the chore. I also believe they were only getting 6 months out of a camera, then again the ride hard with it every day.
For a camera, I use the Canon Elura 50 - very small, digital tape, setady shot and some nice features. Have a LANC controller so I can turn the cam on and off without actually touching it. Allows ,me to put the camera in a padded tank bag or the bike's tail section.
For a mount I made some fork tube clamps and can position the cam behind the screen or elsewhere. I made a cool frame slider mount that shows the front wheel in the shot. Also made some rear facing mounts.
Need to get the fisheye lens so I can get the shot from the dash facing back at the rider. Always wanted to do that.