I have covered a lot of alternative sources of energy with Wind Power and Solar Energy, but nothing is more captivating to me than what has been coming along for several years now as a potential power source for millions of people everywhere.  Completely clean energy that creates no greehouse emissions in it's production.  Energy that is created through the power of waves at the surface of the ocean and currents in the mouths of rivers and bays. 

The NBC clip below says it all. 

This will be come even more important as potential for electricty generation from our nations dams becomes more and more scarce as is published in this recent study.