Google Earth Educational Resources
Google Earth is a free, downloadable application that works as a browser for all sorts of information of Earth.
It uses satellite imagery to grab, spin, pan, tilt and zoom down to any place on Earth.
Students can explore every corner of the globe, measure distances, create their own virtual tours, and share their tours with others.
You can also create and download layers of information and view them in geographic context.
(taken from the West Ed document explaining Google Earth)http://www.evalamar.com/tut_GE.htm