There are a few places to game outside of
DC in Maryland. Unfortunatly the last gamestore that supported
40k in the District closed back in the 90's. There is Dream Wizards by White Flint that has wargaming on Wednesdays only, the crew that manages it is the
http://beltway-gamers.com/forums/, a cool group. They also run tournaments once or twice a year (I got the CyboSkull in the last one!)
There is a
GW Bunker out in Bowie MD that is cool but virtually impossible to get to via public transportation and a bit of a hike if you are living in
DC proper. I think there are some other
GWs around the suburbs as well but I haven't been to them.
Labyrinth Games
http://www.labyrinthgameshop.com/ near Eastern Market will order
GW stuff for you but they don 't really have the space for
40k.
If you have a car and don't mind driving up to Glenn Burnie, near Baltimore (about 45 min to an hour give or take from A.U.) there is DropZone
http://www.dropzone-games.com/. I have only been there once to scout it out with my friend but OMG! It is beautiful, clean, loads of space, huge stock, painting areas, can handle a huge number of gamers. Oh yeah food and clean bathrooms. The only downside is that is it far from
DC and again, no public transport option.
There are a few meetups that do
40k but they seem to be pretty sporadic. But you may be able to find/found a gaming club at AU.