DC checking in, thanks to Twitter:
DC has a pretty good range of shops, and has for a long time, so they've become a bit specialized. All can maintain anything, all can order anything they don't carry, so personal preference is a big factor.
Here's my rundown of ones I know well, but there are a lot I don't know too:
http://www.bicyclespacedc.com/
BicycleSpace near the convention center is owned and staffed by great people who have deep roots in other DC bike shops. Big fans of internally geared hubs and common sense, they also throw a good party and lead some fun social rides. Their head mechanic has the longest beard in DC, and his wizarding skills match.
http://thedailyriderdc.com/
The Daily Rider on H St. NE is owned by enthusiast entrepreneurs who were frustrated that no other shops in DC specialized in nice bikes for everyday useful riding - bikes designed to be ridden in everyday clothing, bikes meant to carry loads, bikes meant to be easy to ride and maintain.
http://revolutioncycles.com/
Revolution Cycles has four locations around the area, with a DC location in Georgetown at the Key Bridge is my go-to general service bike shop. They've been around for a long time, and cover mainstream bike sales and service very well.
http://bicycleproshop.com/
Bicycle Pro Shop (Georgetown at the Key Bridge - yes, a few doors down from Revolution) arguably changed cycling in the USA forever, as one of the very first shops to import lightweight European racing bikes in large numbers back in the 70s. It's a bit more mainstream now, but it's still the only shop I go to that stocks high-end components. (Second location in Alexandria VA).
http://citybikes.com/
CityBikes has two DC stores, one in Adams Morgan and one on Capitol Hill (where I worked a second job for a while). This is DC's older mainstream bike shop, dating back to the 80s. Because of my insider information I'll hold back my opinion here - but they've been good enough at what they do for long enough that you can read between the lines of the Yelp reviews.
I don't shop often enough at the following places to really say one way or another, but you should find out about Capitol Hill Bikes (8th St. SE - doors away from that CityBikes), CycleLife (Georgetown waterfront), Big Wheel Bikes (Georgetown waterfront, Alexandria & Arlington VA), Spokes Etc. (Alexandria I think) The Bike Rack, and District Hardware - plus a lot more in the surrounding communities. Here's a directory of shops in and around DC that offer a discount for Washington Area Bicyclist Association members - can be well worth the $35 annual fee:
http://www.waba.org/resources/shops.php
