The Emma McCrary trail is a nice singletrack that was built by many volunteers and spearheaded by the Mountain Bikers of Santa Cruz. It is a beginner friendly trail (no more than 7% grade, but usually much less than that) that runs from the trailhead at the end of Golf Course Drive to the intersection of the U-con Trail
and Rincon Trail.
Descending, Emma McCrary Trail is particularly yummy, as it is very flowy with many nicely bermed sections. This trail runs through lush groves of redwood trees.