I am fortunate to learn of a number of great websites from the people I follow in Twitter. Today "cliotech" (be sure to check out her excellent blog) posted a link to this one, Teaching with Google Earth.
Topics include: What is Google Earth?
Becoming Familiar with Google Earth
Why Teach With Google Earth?
How to Teach With Google Earth
Working with KML
Google Earth API
Examples of Google Earth Activities
Complete List of Google Earth Activities
I'll need lots more time to explore this site, but it looks very promising!