Any good riding in this area? I may have a job opportunity that would entail a move there. Am I going to like it???

Here ya' go! Just after I mention this part of the site, a few people respond. Anyhoo...more will chime in, I'm sure, after hte weekend.
In the meantime, check out www.bikepptc.org (http://www.bikepptc.org) or www.waba.org (http://www.waba.org) PPTC is a huge cycling group. My rides at all levels meet w/in 30-40 min of Ashburn (you'll soon learn that that is not a huge amount of time).

I live in Ashburn and bike to Reston for work via the W&OD (http://www.wodfriends.org/). Head west on the trail for some hills out past Leesburg and East for the city. Not my thing, but from what I've heard the best MTB trails are in Fairfax county which aren't too far but unless you want to pedal 20+ miles on knobbies I think you have to drive.