Here are some spots I like.
Go up Hiway 50 to kyburz then another 5 miles to Wrights lake road. Go the 8 miles to Wrights lake, then another 1/2 mile to Dark lake and there you will find the Barretts Jeep trail. It is six miles of pretty challenging trerrain. Not as difficult as Rubicon or Sierra trek, but a nice challenge up to a a gorgeous Barrett Lake. 3 1/2 hours from bay area
If you have dirt bikes or quads, head up to Stonyford in Mendocino National Forest. Go interstate 505 in vacaville, then interstate 5 to Williams then to Maxwell, then take turnoff to go to Stonyford. About 8 miles past Stonyford is the Fouts spring campground. Wide open trails for bike riding. Some of the best riding anywhere. 3 1/2 hours from bay area
Another fun, but not too challenging area is out of Fraser flat campground, Just before you get to Pinecrest Lake out of Sonora on hiway 108. Washed out forest roads take you to Stanislaus river and nice trout fishing. 3 1/2 hours from bay area