Check this out.
http://www.rexresearch.com/meg/meg.htm
It's called the "Motionless Electromagnetic Generator", and it produces electricity for "free". The one shown in the picture produces 6.764W from an input power of 3.25W. More efficient versions have also been built
This isn't a hoax, a patent was actually awarded for the device back in 2002. To get a patent, your idea has got to work...
From a scientific point of view, I haven't read much, but apparently the device works because it makes use of longitudinal electromagnetic waves. Energy is taken from this resource by the device and turned into seemingly "free" electricity.
With a bit of extra circuitry it should be possible to loop some of the output from the device back into the input, thereby creating a standalone power plant which produces electricity indefinately.
Looks pretty easy to build as well...