It looks like the 2006 version of the Cougar Mountain classic will be held in mid July instead of early September. The date was most likely to moved to keep its place as the "last chance to qualify for NORBA National Championship finals" that it held last year. The event will be held at the same venue (Infineon Raceway in near Napa) and have what appears to be the same events.
I raced XC and MTX last year and had a great time, although the pro attendance was sparse due to some scheduling conflicts. Although the XC course was mostly hard-pack rolling hills with very little technical descents, the mountain cross (MTX) was a nice mix of jumps and berms. Oh, Sierra Nevada Brewery also showed up, which made it all worthwhile.
Event: Cougar Mountain Classic
Dates: July 14 - 16, 2006
Location: Infineon Raceway (Sonoma, CA)
Competition: XC, DH, MTX, 8HR Marathon
Cost: unknown (last year between $30 - $55)
UPDATE (05/15/06): Cougar Mountain has been cancelled and replaced with the US MTB National Championship. See a list of the new events here.