Keith Veronese at io9 has a good backgrounder on the potential for Helium-3 (3He) to be used in future 2nd generation fusion as a clean solution to Earth's looming energy conundrum. Veronese's essay over-simplifies a bit - which is ok by me given that it's intended for a broad audience - but overall does a pretty good job of hitting the major points. Not too enthusiastic, not too skeptical... just about right.
If you watched the movie Moon, you remember Helium-3 as the substance Sam Bell was sending back to Earth, during his onerous three year tenure on the Sarang lunar base. Helium-3 is not a piece of science fiction, but an isotope of helium that really could provide for all of our energy needs in the future. With absolutely no pollution.
The Helium-3 fusion process is not simply theoretical — the University of Wisconsin-Madison Fusion Technology Institute successfully performed fusion experiments combining two molecules of Helium-3. Estimates place the efficiency of Helium-3 fusion reactions at seventy percent, out-pacing coal and natural gas electricity generation by twenty percent.
Obtaining helium-3 from lunar regolith will not be an easy task. Best estimates of Helium-3 content place it at 50 parts per billion in lunar soil, calling for the refining of millions of tons of lunar soil before gathering enough Helium-3 to be useful in fusion reactions on Earth. Should we be so eager to strip mine the moon and destroy its surface to provide a clean energy source for Earth?
The first nation (or conglomeration of nations) to establish a Moon colony and begin mining operations will likely set the standard for control of resources on the Moon, especially if exploration of the Western world plays a role as precedent. Let's hope the nation has kind, altruistic motives at hand - otherwise, we might be better off with a private company (as in Moon) making it to the Moon first, with an intention of harvesting its resources.