Men's Fitness picked five American bars for the beer geek. In Washington D.C., they send you to Brickskeller, famous for having a binder with 1,000 different bottles divided by region. What they fail to mention: most often Brickskeller is out of at least half. Another option, at least if you like Belgian brews, is Brasserie Beck, which also has tasty beer-friendly foods (pork, cabbage confit, mussles).
In Brooklyn, they recommend Spuyten Duyvil. Under the same ownership, Spuyten Duyvil Grocery is a tiny shop crammed with imported beers that come with tales of the beer's origins, compliments of the shopkeepers.