Biking 
Maintenance and upgrade information as well as safety information on the bikes and the sport of mountain biking. Covers downhill, 4cross, and dirt jumping.
http://www.mountainbikeinfo.co.uk/
Bike news, race results, reviews of the latest cycling parts and accessory.
http://www.mountainbikingnews.com/
Mountain biking community based in the San Francisco Bay Area that caters to bike riders in Northern California. Includes reviews, pictures, videos, event and race coverage, a forum, and daily rides
http://www.msdhw.com/