I'm going to Wasington, D.C. next month for the DC PHP conference. I've been there once before with family and enjoyed it a lot but this time I'm going alone and I'm wondering what there is to do in the evening. Seems like all the museums close around 7 or 7:30 and I don't remember there being much else to do at night but walk around looking at the monuments. (Which is fun, but I've got 3 or 4 nights to fill) Any thoughts? Any unique geeky things I shouldn't miss while I'm in town? (I've already been to the Air & Space museum.) Is there an SR-71 parked anywhere nearby? That would be worth a rental car.