I have...
Put in a lot of saddle time at Blue Knob. The ski area runs might be more what you're looking for, but the singletrack in the State Park area is sweet. The ranger's office at the bottom of the State Park (near the pool) has free maps. There's a 17 mile singletrack called Turkey Run (or Turkey something) that can make for a great loop if you ride the part betwen the ski area and the Burnt House picnic area. Definitely get a map though, as the trails weren't well marked when we used to ride there.