I just bought an MD 80 Mini DV camera for an amazingly low price of under £10 pounds including postage from Hong Kong. (Don't think they've been mentioned before?)
It's about the size of a bluetooth headset, or the size of your thumb. The results were surprising good. Easily good enough for You Tube, or better. I used a 4 gig micro card with it and got about 53 minutes recording time. The internal rechargeable battery is probably only good for an hour anyway. Apparently class 4, which has a faster write speed, may work better than some cheaper cards. That's what I went for anyway. With reasonable sound too, and 720 x 480 res (it says?) Format is AVI, so you can even edit in Windows free Moviemaker
Great little camera for helmet mounting, etc. It's so small it can easily be clipped to your helmet or handlebars
Comes with a few mounting brackets, including one that clips on, driver disc, lanyard, etc. The instructions are very badly translated, though it's not difficult to figure out. There are quite a few on e bay, some even cheaper, but I bought direct from what looked like a reputable supplier in Hong Kong. I think there are some bad copies out there.
Haven't had a chance to try it while riding my motorbike.
Try you tube there are some good videos? on it.
Great fun potential?