I know I'm reaching pretty far back, but just saw a few people talking about vintage. I wish I could be more positive about DC, but really I didn't see any vintage stores that are worthwhile or even compare to other cities vintage selection.
Meeps and Annie Creamcheese get talked about a lot, but are really subpar if you want good quality vintage (not just designer, but quality of the item itself in materials, rarity etc). Meeps also moved recently, and I have not been but prior to that I wasn't impressed.
Annie Creamcheese apparently was huge and wonderful in...Arlington? But I went to the new DC store shortly after it opened and was very disappointed. It was full of 13 year olds going "Oh my GOD, this store is soo COOL!" (verbatim) and grabbing at things. One of the salespeople apologized to me about it, haha. Its also tiny space wise. And the dressing room smelled of BO and pee, I was like holy hell! WTF happened in here?
There is also a highly over priced designer side of the store, with a far more interesting accessories case. On the other are cheapy castaways, you can find anywhere and I was not impressed. Prices for this side are ok though. Saw a MJ jean skirt for about 45? Not too bad. I spoke to the woman that owns the store, she said she gets new stuff in on Tuesdays I think? And she came back from Las Vegas with more finds. Nicole Richie apparently got Joel to buy her some sunglasses from there as well.
I read about the Georgetown Fleamarket but never went. Maybe you'd find more vintage there? How about any sellers at Eastern Market. Did they rebuild it?