Washington, DC is a very exciting place. If you have free time, I recommend visiting the
Smithsonian Institution, my favorite spots being the outdoor sculpture gardens (near the Hirshhorn), Natural History Museum, Air and Space Museum, the National Zoo, and the National Botanical Gardens. The monuments are also pretty nice to visit.
I love walking around Georgetown (in DC) and Old Town Alexandria. We'll update this later on with things to do in Fairfax County, where we live and also where the wedding will be.
There will be fun events (besides our wedding!) in the area over the weekend to celebrate Memorial Day.
Click here for a link to Memorial Day events in Washington, DC, although it has information for 2007. We'll update for 2008 as soon as possible.
The City of Vienna, VA has a three day festival for Memorial Day Weekend,
click here for information.