Another suggestion for those who are historically inclined, the Independence Hall tour is quick moving and informative. You sit in the same seats as the delegates for the Constitutional Convention.
I recommend (if you go there) that JGeoff sit in Madison's seat...he had a beverage holder installed on the right arm rest so he wouldn't spill his drink.
The most memorable tid bit was the description of the inauguration of John Adams, which was attended by correspondents throughout the world, who could not imagine a peaceful transferral of power and were amazed when Washington did not arrive with a militia to keep power. Washington merely walked home alone to his Philadelphia lodging after the inaugural.