United States Geological Survey (USGS)

Another US-centric resource dating back to 1879. The in-depth geological content is aimed at an audience with a scientific background. The 'Energy Resources' program focuses on the understanding of the process which lead to the presence of hydrocarbon resources on US soil and beyond. But for specific queries on issues such as non-conventional energy sources this is a comprehensive resource.

The site is updated less regularly than others. But data are brought to life in maps of the US and beyond. There is a database of fairly dense publications, and the data finder and interactive Energy Vision tools need some prior understanding to interpret properly even if information is graphically presented. But some research is condensed into easily digestible fact sheets for non-experts. The Twitter feed as @USGS also does an admirable job of trying to liven up the hard science.

http://energy.usgs.gov/