Where would you go in the National Mall?

I'm going to be in D.C. with a friend who's never been into the city before (!) to check out the National Cherry Blossom Festival, and look at major monuments. I was hoping to stay in the National Mall/Smithsonian area (staying between Lincoln and the Capitol). Aside from the obvious (Jefferson, Washington, Lincoln, Vietnam) where would you take a friend who had never been there before?