Mount Tam is probably one of the most recognized name in mountain biking when it comes to riding places. Mount Tam riders have defined, over the years, how bikes sould be built and ridden. It is visable from anywhere in the Bay Area, so it attracts a lot of attention. Mountain biking is not legal on virtually any of the singletrack on the mountain, but it is allowed on the many fire roads. Eldridge Grade and Railroad Grade are the main roads to the peak, but many, many more exist all over the mountain.
Every rider in the Bay Area knows about China Camp. It has some of the only legal public access single track in the area. China Camp is fun and easy. Take a new rider to China Camp and show them the ropes.
Most of the ridinding areas around Fairfax are under the jurisdiction of either State Parks, Marin County Open Space, or Marin County Water District.
Camp Tamarancho, owned by the Boy Scouts of America and access supervised by the Friends of Tamarancho. One of the coolest things about Tamarancho is that bicycles are not allowed on the fire roads, only single track. Annual or day passes are required to use the camp. Talk to Brian about how to get your hands on one.
Annadel State Park is located up in Santa Rosa. It is a bit of a drive from Fairfax, but worth every minute. Annadel is the best example there is about how mountainbikes, horses and hikers can share access to a lot of incredible single track. You are guarenteed to love your ride at Annadel.
Home of the Repack Downhill race. Pine mountain is the lonely little brother to Mount Tam. If you are sick of the crowds, take a ride up Pine Mountain. A nice back door to Pine Mountain is threw Camp Tamarancho.