If someone did care to start a sticky with "what to do in NOVA", I'll add suggestions based off of what people here have suggested, and what I ended up doing with my buddy.
All the stuff in DC:
National Archives, the National Mall, the Smithsonian museums, WWII, Korea, WWI and presidential monuments, the Capitol building, etc. TONS to do in DC and getting around on the Metro isn't difficult.
If there's a Nationals game, that's fun to go to (we went to the Nats vs Cardinals game last night, it was fun and the Nats won on an awesome double play)
Harpers Ferry is a neat little town to visit.
Gettysburg, PA isn't to far away
Mount Vernon
Manassas
I'm sure this list is not near inclusive. There's tons of things to see around this area. I fly home on Monday, so today we're going up to Gettysburg, then tomorrow we're going to visit Mount Vernon and then take my buddy's son to drive gokarts. I only wish the weather had been a bit warmer!