There is also a new race from the BikeMonkey / Global Biorhythm Events (Tahoe 100, 24 hours of Cool) team:
This year, Bike Monkey will partner with Global Biorhythm Events to produce a new Northern California Ultra Endurance Points series–The Leave No Trace Ultra MTB series. Bike Monkey will produce two endurance events - Boggs 8 Hour on March 28th, and the Sonoma 100 on May 16th. Details on the Sonoma 100 will be coming shortly. It very well may become one of the toughest 100 mile endurance races on record with as much as 15,000′ or more of climbing. and nearly 80+% of the course competed on singletrack.