Make Magazine, volume 9, has a good article on perpetual motion machines, along with other kinds of inventions usually regarded as "fringe" by the scientific community. I'm highly skeptical that these folks have found a way to get something for nothing, or that our knowledge of the physics of magnetism is as incomplete as these folks claim. But I suppose, as with Ephraim Fischbach's "fifth force" and various cold fusion claims that pop up every few years, we'll just have to let the scientific process run its course.
As Yvan says, we've got a good source of free power already, in the form of a huge fusion generator only 93 million miles away, beaming energy constantly at the entire Earth. Investing a bit more time and money in developing ways to make solar power more efficient and inexpensive would probably be a better choice.