NASA - dynamically updated information, images and videos from various online NASA sources. Users can access NASA countdown clocks, the NASA Image of the Day, Astronomy Image of the Day, online videos
NASA Lunar Electric Rover Simulator - experience what it might be like to ride a rover around a lunar outpost!
NASA 3D Sun - rotate the sun and see all views. Look at flares and sunspots up close. Three-dimensional version constructed from real-time photos & movies.
To me the big benefit of the ITouch and IPad is that they are easy to travel with. Students can be working anywhere in the building and move to a new site. This would greatly add to field trips and field work where students could be researching additional information in relation to what they are physically experiencing. They would also be able to record data in a dynamic way (instantly plugging data into a graph, averaging data in a spreadsheet, etc...)
