David Tryse continues to offer great methods for visualizing data with Google Earth. This time he has produced a great free tool called the KMLFactBook . The KMLFactbook utilizes data available from the CIA World Factbook to let you pick and choose geographical-based data about the world and see 2D and 3D graphs of the data by country on either a 2D Google Map or use the 3D Google Earth plugin. You can also generate a KML file to view the data directly within Google Earth. There is a massive amount of data here to play with and get some interesting perspective about how things are going on our planet. Not only that, but the KMLFactbook provides details on how to upload your own datasets to generate other visualizations using simple spreadsheet formats.
World Population Data
David had previously produced some visualizations for disappearing forests around the world, and the Edge of Existence collections in the Google Earth Outreach showcase. He also recommends the Thematic Mapping Engine by Björn Sandvik which uses similar techniques.