You should try to see the Newseum in Rosslyn. Quite the place. Wiil close in March because they are going to build a new one at 7th and Pa. Ave. But that will be a 2-3 year project. Metro is the way to go and it's an easy hop to the Pentagon from there.
Union Station has really changed in the last 12 years.
Even if you don't care about plants, the Botanical Gardens just reopened after a 3 year renovation and it is great..and free.
Back over on Pa Ave you should peek in the Reagan Building and next to it the Old Post Office (Take the elevator to Z top..) Oh, and next to Union Station there is a new Post Office Museum.
I always tell people to try and see the National Building Museum at 4th and F NW. Beautiful. Right next to it is the National Police Memorial where they add the names of fallen heros once a year.
Just talking about it makes me want to go play tourist, which I do quite often. Everything I mentioned is FREE. Metro is the way to get around unless you are hoofing it on the Mall and Pa ave.
Hope that helps.
Hmmmm? It's good if you have only been alive for the last 15 years or so. Otherwise, it's all CNN reporting - I thought it was terribly boring!