Ten years ago I would've said you were out of luck.
However, since then, the Ashburn area has EXPLODED and gotten a lot bigger. It sounds corny, but you might consider shopping around for a gym - usually you can meet other people similar to yourself, or make new friends.
If you have particular interests (reading/poetry/horseback riding/working on cars/playing an instrument/shooting guns/karaoke/whatever/etc) there are a lot of groups in the NOVA area for all sorts of niches, just jump on Google.
~Brad