Recently, a high school geography teacher, Josh Williams, contacted me to share his website GE Teach. GE Teach is built around the Google Earth browser plug-in. The purpose of the site is to help teachers develop lessons in which students explore spatial distributions.
Visitors to GE Teach can select from a variety of physical geography and human geography layers to display and explore. A fantastic feature of GE Teach is the option use the "two Earths" mode to show two maps side-by-side. In the image below (click to view full size) you can see that I have used the Earth on the left to view climate regions and the Earth on the right to view population density. The "two Earths" mode could be useful for prompting students to make comparisons and or correlations between two maps.