Bike trails in Bidwell Park, from the city web site [pdf]
Chico Velo: Bike rides in Chico area, links to local bike stores and much more.
Chico Mountain Bikers: Bike rides in Chico and other mountain biking areas, bike shop info, Park trail closure info. They also help maintain Upper Park trails.
Chico State Cycling Club: A local mountain biking group.