Air and Space Museum

One of the places I never fail to visit every year is the Steven F. Udvar-Hazy Center - sometimes referred to as the Dulles Annex of the Smithsonian Air and Space Museum. I never cease to be amazed at the aviation history that is contained within this center. Twelve bucks a carload to get in.

Go check out the Concorde and the Enola Gay (B29).

Here's two places with good info:

Smithsonian Website
Wikipedia

It also has a wonderful IMAX theatre.