As part of the Fairfax Fat Tire Festival, the Friends of Tamarancho MTB race will be held on May 25, 2008. It looks like a similar course to last year: "Race course will use camp roads and trails, including Broken Dam trail and Serpentine trail counter-clockwise, as well as some race day only routes. Multiple lap race. 6 Mile lap. Beginners 1 Lap, Sport 2 Laps, Elite 3 Laps." Find more information from last year's race in the archives.
Thanks to Alex for the heads up.