We have some tours going on tomorrow around DC, including the Capitol, National Archives, and Congressional Cemetery. (please RSVP for these)
http://wikimania2012.wikimedia.org/wiki/Tours
Time permitting, we can walk around the National Mall and take you to the sculpture garden at the National Gallery of Art (or any other requests?). The weather is supposed to be a lovely with a high temperature of ~30 C (~86 F).
On Friday night, after the education meetup, I'm happy to take people around the Georgetown neighborhood on an informal walking tour. :)
Feel free to make additional sections on the tour page for self organizing groups to go sightseeing places.
Cheers, Katie