Real World Math is a great resource for teachers who would like to explore uses of Google Earth in mathematics lessons. A few years ago I wrote a couple of blog posts about Real World Math. Since I wrote those posts more lessons and tutorials have been added to Real World Math.
Real World Math, designed by Thomas Petra, uses Google Earth as the centerpiece of mathematics lessons. Real World Math has the lesson plans divided into five categories; project-based learning, concept lessons, measurement lessons, exploratory lessons, and space lessons. The space lessons take advantage of the Moon, Mars, and Sky views in Google Earth. If you've never used Google Earth, Real World has a large collection of tutorial videos that you can view on the website or inside of Google Earth.