Good beginner/intermediate type of ride that never strays far from civilization. Starting point is at the Rainbow Bridge near Old Folsom at which point you'll cross the bridge and head north on the American River Bike trail. A dirt path will immediately veer off to the right to reveal some nice single track. It will weave on and off the paved trail and eventually end as you make the climb up to Beals Point on the pavement. In the map above (referring to my website), the red trail represents the dirt/off road and the yellow trail is pavement. Contuniuing on, the trail will hug the side of the lake turning to gravel then dirt by the time you reach 5th camera up. At the six mile mark you'll reach the park and boat ramps. There are some single track trails off to the left. Eventually the trails will head off to the west where there are many interlocking single track trails. There really is no right or wrong way to go. I didn't even hit all of them on this ride. Pretty safe to explore as they don't stray away from this general area...you just can't get any further without hiking. This time of year (spring) some of the trails were under water as the 8th pic up shows. You could also drive to Granite Bay or Beals Point as starting point for shorter rides.
Hwy 50 to Folsom Blvd exit. Head north until you cross the bridge then take the next right (Greenback). Cross the small bridge and look for parking on the right side of the street.
http://www.singletracks.com/item.php?c=1&i=755