I'll second Rob's opinion for the Go Pro HD Hero. It's got a waterproof housing, is small and is easily attached to many different things. We use them all the time for our video needs and they compliment the full HD commercial cams we run on a regular basis.
If you watch the X Games on ESPN or any of the extreme sports, the Go Pro's are basically the only thing used unless the are broadcasting a signal, in which case, the Go Pro isn't an option.
We attach them to the side of boats, top of helmets, side of bows, windshield of cars, etc. Makes for some really cool video, for sure!