Re: Aviation, airplanes

If you have access to a car, there is a new Marine Corps Museum at Quantico (where else?). I do recall some airplanes or helicopters there. It is excellent and free.

In the same vein, the Navy has a museum at the Navy Yard, which is accessible via the subway. It is not a bad collection, though it is a little dated. Of course, more ship stuff than airplanes, but both are present.

There is a big air show at Andrews AFB, open to the public. Not sure when it is.

Re: non-art

Also: National Firearms Museum at NRA headquarters in Fairfax. Done in historical context, including President Teddy Roosevelt's involvement.

Charlottesville: Monticello and University of Virginia

The embassies (there are well over 100 of them) have various programs. You can catch concerts, movies, lectures on the various countries.

If you are into historical homes, there are many open for touring. One that I went to recently, and was impressed, is the Frederick Douglass home, run by the National Park Service, in the SE part of Washington.