The annual book fair, held every October, is well worth a visit. There’s a great collection of used books with a trend towards foreign languages, foreign policy, history and diplomacy(as you might expect at the State Department.) You have to be quick, however, because it is only open to the public for one weekend. In 2011, that’s October 22 – 23, 10:00AM-4:00PM. And most everything is half price on the last day! Details here: