This was a fun event last year (shamelessly lifted from the SWIMBA website):

Join in a day of family-friendly mountain biking and hiking at Bogus Basin on Saturday, July 25th, 2009. Food and beverages will be available for purchase from 10:00 AM until 5:00 PM. Deer Point Chairlift Number One will be operating from 10:00 AM until 4:00 PM. Lift tickets will be a available for purchase on the day of the event, and riders must sign a liability waiver. Mountain bikers must wear helmets to ride the lift.

Beginner mountain bike trails are located near Frontier Point Lodge on the Shafer Butte trail system. No tickets are required to access these trails.

For more information, please visit the Bogus Basin website: http://www.bogusbasin.org/