Hey theres a little new place in Fairfax called Oasis bike works (
www.oasisbikeworks.com). They're really a personal shop. They mainly cater to the George Mason student pop. but they have a good direction. I just recently bought a fixie from Kona through them, and Dave(owner/partner) shaved some of the price and is helping me personalize the bike( flat narrow bars, pedals) they don't carry many bieks in the shop but they can easily find what you want, and won't charge extra either. You pay for the parts and they'll put them on for little or no mechanic's surcharge.
Oh and they're huge on bike commuters.