El Corte de Madera - Also known as Skeggs point for the primary trail head in this park ECdM is located on Skyline Boulevard (Highway 35) South of San Francisco. This trail system features lots of Singletrack, tons of extremely fast fireroad descents and many different routes over miles of trails. There are more than 25 miles of trails in this park system. Perhaps the only downside to this trail is that it is a very heavily used by area mountain bikers and hikers.
Forest of Nisene Marks - A beautiful forest ride along a well travelled fire road. This is a great trail to take your kids or a beginning rider to.
Fort Ord/ Sea Otter Racecourse - Just inland of Monterey and adjacent to the Laguna Seca Raceway are the remnants of the Fort Ord Military Base which were given the the Bureau of Land Management. Now there are many miles of multi use trails including miles of singletrack engineered with mountain bikers in mind. This is where the Sea Otter Classic is held every year.
Henry Coe - Beautiful suroundings, very few people, plus miles and miles of great singletrack. I can't wait to go back.
Pacheco Pass - Located along Highway 50 between Gilroy and Santa Nella is Pacheco Pass State Park. There are about 20 miles of trails in the park, mostly smooth singletrack with very little rocky/ technical riding.] The trail has plenty of climbing and extremely fast descending down singletrack and overgrown fireroads.
Saratoga Gap Trail - Although this trail doesn't offer much for technical riders or downhillers it is an excellent cross coutry ride with some fun trails, lots of climbing, and cool shady forest.
UC Santa Cruz - A variety of trails near the UCSC campus
Whittmore Gulch - Also called Purisma Creek. This is an out-and-back off of Highway 35 through some beautiful wooded areas.
Wilder Ranch - Along highway 1 this trailsystem has about 40 miles of trails. Most of the trails are wide multi-purpose trails but there is quite a bit of singletrack as well.