Cool little video about history of mountain bike riding from "Klunkerz: A Film About Mountain Bike History"
more about it:
"Klunkerz is the award-winning documentary on off-road cycling, focusing on the San Francisco Bay Area in the late 1960s and 1970s. The film features interviews with the pioneers of the sport and the more obscure characters who influenced them. The film also contains a great deal of archival footage and photographs that have never been seen before. The film is available at www.klunkerz.com."