Here in Ontario, most power comes from Nuclear (Hydro takes 2nd place). I believe all fossil fuel plants are scheduled to be shut down in 2014.
I should have qualified that with "most power in the US" 
I know very little about this stuff outside of what I learned from this project, which was very US-focused, even if we had some Canadian teams. I am a software engineer, and don't think about these things very often I now know a hell of a lot about how to develop a hybrid control system, but very little about how to... well... change a tire.