LocaleTrends uses heat maps to present a detailed view of important housing, education, employment and demographic trends in distinct geographic areas in the USA. The site has a number of Google Maps for each state or you can select regions within each state.
For each area it is possible to view heat maps showing real estate data, public school test scores, demographics and employment data. The home page shows the most viewed maps on the site and you can navigate to distinct areas via two drop down menus.
Via: Programmable Web