Hey Buzzwire! With the number of MTBs being sold out of the shops around here you would think it would be promoted more around here. I haven't ridden offroad in years, but asking around the bike shops is always a good idea. If they don't have a group that rides regularly they should be able to tell you how to contact some.
Back in the day, well back in MY day, Cave Run Lake in KY was a good place to ride.