RENEWABLE ENERGY TOOLS
Have you ever wondered how your local energy company is providing you power? Are they really using as many renewable resources as they claim? Are they using any? Here's a great tool to help you find out...provided by the fine folks at the EPA: http://www.epa.gov/RDEE/energy-and-you/how-clean.html
If you've been thinking about adding a solar or wind system to your house or property, the National Renewable Energy Laboratory (NREL) has some tools to help you figure out how well your area is suited for such renewable energy production. You can find maps, analysis tools and GIS Data here : http://www.nrel.gov/gis/
Another renewable energy mapping guide from the EPA here, their interactive mapping tool . You can view the EPA's information about siting renewable energy on contaminated land and mining sites, alongside other information contained in Google Earth.
SOLAR and WIND ENERGY TOOLS
Here's a handy calculator to help you determine a few different renewable energy sources in your area like solar energy, wind power, and solar hot water: Solar and Wind estimator
Here's a wind energy resource map from US Dept. of Energy: http://www.windpoweringamerica.gov/wind_maps.asp
This one's a bit more technical, but might be of use - the theoretical ethanol yield calculator .
Interested in Hydropower? Here's a virtual hydropower prospector tool .