There is a bar off centreville rd and route 50. I think its name is backyard bar and grill. Its one of the few places I know around there. Its right next to where the blockbuster is (or used to be, been awhile since I been up there.)
Theres both of the air and space museums. There is the one which is actually on the farside of the airport, and then there is the other which is in downtown D.C. The one on the airport has an IMAX, might be something good in there.
Other than that take your pick of monuments in D.C.