We use a Drift Innovation HD camera, helmet mounted with it's remote handlebar mounted. It is hardly noticeable and works better at getting 'candid' footage while riding. We have captured conversations with service people, exchanges with small children in Morocco when we would be giving out pencils, etc. that you can't get with a bike mounted camera, and the Go Pro sticks out like a sore thumb on a helmet.
There is also Contour HD cameras which have now come down in price.
Get something that mounts as high as possible for great footage, low mounted units just don't show the terrain as well.