One of the apps for iPod Touch recently used in an astronomy class at the high school level is Moon Globe. There is an awesome app review of this at the following link:
So if you are an astronomy teacher or other science teacher who teaches about the moon, this app is for you! Some of the other apps used were 3D Sun, NASA, Space Images and Stars.
Above also are pics of some of the students in Mr. Hough's class using the apps on the iPod Touches.