Social Explorer lets users dig through all kinds of demographic and environmental data.  In honor of Earth Day, you can take a look at carbon emissions data.  This data comes from a collaboration with the Vulcan Project, a NASA/Department of Energy funded effort based at Purdue University.  The Vulcan Project has quantified US fossil fuel carbon dioxide (CO2) emissions at space and time scales much finer than has been achieved in the past.

Carbon Emissions Data (2002)

Social Explorer users can explore carbon emissions data for 2002 here (or click the map) too look at emissions around the nation and in your own town.

With American Community Survey data, you can also look at home heating fuels.  Here is a map of where solar energy is used.

Solar Energy Use (American Community Survey 2005-09)

As you can see, this isn't a widely-used resource yet, but if you click around the map you can see pockets of solar energy in states like Colorado, New Mexico, Texas and even Illinois.

Check out the data behind the environmental policy debates, and then do something nice for the planet on Earth Day (and every day).