The Downieville Classic, NorCal's premier downhill competition, has set the tentative dates for the 2006 edition as July 28th - 30th. They are still awaiting Forest and County approval before committing to the dates.
Downieville features a downhill race "dropping 4,700 vertical feet in 15 miles" as well as a cross country point-to-point race "twenty eight RUGGED miles through California’s richest and most scenic gold country" with " 4,400’ ascent with 5,700’ descent." There are also other events at the three days festival.
UPDATE (3/2/06): The dates and courses have been finalized. See here for more info.