Murder capital of the US, but on my last trip there I did the following
Lincoln & Washington Memorials & Reflecting Pool, Sunny afternoon's perfect for a visit.
The Wall (Vietnam Veteran Memorial) - Best at night, it gives it an even more austere air, if it's just been raining the ambience is spooky
Arlington Cemetary & JFK's eternal flame - may be closed on certain dates though, and is then restricted to relatives of people buried there.
The Smithsonian National Air and Space Museum -
http://www.nasm.si.edu/ (There's loads of Smitsonian sites in DC
http://www.si.edu/museums/ )
Shopping at Tysons Corner
Couple of dinners in Georgetown.
Do Georgetown at least one night during the trip. Not necessarily on the weekend.
I really liked the place, as long as you get past the fact that it's a town focussed on politics.
Can I come too?
Jason