Not really Fairfax, it is a hike but check out Markoff's Haunted Forest.
http://web.mac.com/markoff/iWeb/MHF/WELCOME.html
I went last year with my girlfriend and it was an awesome time. Coming from Fairfax (if you have time) I would reccommend taking White's Ferry if you never have. It was my first time on it and I just thought it was really cool. Plus once you get off the Ferry you make like one turn and you are there.
I wish I could be going this year but I am in Chicago for school. Booo. I actually miss Fairfax. Who would ever of thought someone could do that. Hrmph.