If you check out my Youtube account you'll notice that I have a lot of riding videos.
Using different cameras(Olympus 810 compact, Samsung HZ30W compact?,
Nikon P100 bridge, GoPro HD, ContourGPS), using different mounting positions(helmet,
fork, handlebars, rear triangle, handheld). I think how the camera is mounted makes a
big difference; the more solid, tight the mounting is - the more stable your shots will be.
Also, the sports oriented cams(GoPro, Contour, etc.) don't have a lens that zoom in and
out that adds to the vibration. Before you spend any money on other mounts or cameras,
I would suggest to add some strips of inner tube to whatever setup you have now and
see how it goes.
HOMEMADE CONTOUR MOUNT1 by
1nterceptor, on Flickr
http://www.youtube.com/watch?v=-oK7zbLmm4Q