On a rainy Sunday morning we went to the American Museum of Natural History (setting for the movie A Night at the Museum).
They have a brilliant guide to the museum iPhone app. There are wireless access points all around the museum that determine your location and you can use the app to take a highlights tour, find out more about popular exhibits, or just navigate the museum with the map.
Most exhibits at the museum are reproductions, I guess so kids can touch and play, but that does make it a bit less interesting.
A few pics: