I was excited to see today via Slashdot that Google Earth has added a Sky feature to use within the product. It allows you to take 3-D journeys through stars, constellations and galaxies. There is all sorts of potential for teacher and student use during the school year.
Here are some helpful websites for users:
Sky: Educational tours (Made by Google Earth users)
Google Earth Blog
Ogle Earth
EasterKiwi 