This weekend I visited the Maryland Science Center and was very impressed with an interactive table that had a computer screen projected onto it. Navigation was controlled by tilting the table and you could zoom in on objects by twisting the table. See the video below to see the interactive table screen in action. Forgive the quality of the video, lighting was not in my favor.
Here are some more interactive surfaces being used at museums around the world.
Emakhosini Museum, South Africa
The Adventure Science Center in Nashville, Tennessee
Coimbra's Science Museum, Portugal
Here is also an interesting video by Adobe on the future of multitouch.