Rock Candy Mountain/Capitol Forest. My buddies and I go down there quite a bit since it's really close to Ft. Lewis. There are tons of trails for atv's/dirt bikes and lots of places to get your truck stuck also. The view from the top is pretty great as well.

Driving directions: Take I-5 south from Tacoma. In Olympia, take hiway 101 north about 5 miles. Then take hiway 8 west about 4 miles. Look for a left turn into Rock Candy Mountain parking lot.