So, you've been reading a lot about Global Warming and other environmental topics and you're interested in finding out just how much the power in your area pollutes. However, you're interested in more than just Carbon load, since although you may not believe in Global Warming, you are pretty certain that Sulfur Dioxide isn't your friend (remember acid rain) and you're not too keen on mercury either. Well, the EPA has the solution to your problem.
eGRID provides data from 2000 (new data from 2002 and 2004 are in the process of being added and should be online by September) about power generation and emissions throughout the US. You can look up information about your particular area of the country or check out the summary maps (which show that about half of Virginia's power is generated from coal and most of the rest of it from nuclear, whereas 75% of Washington State's power is generated by Hydro).
If you're really curious, you can download the databases directly and use them for your own nefarious purposes.