Baltimore's Inner Harbor is great. I always end up at Tir Na Nog when I go up to Aberdeen (which is a lot).

If you like museums, you could spend a few days in DC alone. Hell, you could spend a few days going through the Smithsonians (my favorite is Air & Space - shocking, I know). Arlington National Cemetery (especially if you see the changing of the guards at the Tomb of the Unknowns) and the National Mall are awe inspiring.

Boston is a great city to hang out in. Maine is absolutely gorgeous. Philly has some cool museums.

The right coast is full of places to visit, you really can't go wrong doing a trip like that.