An open mind is a good thing--just not so open that one's brain falls out.
Most of the "physics" arguments presented on the freeenergy.co.uk site appear to address physics from a pop-science-level understanding of physics at best. Now, I'm no physicist, but I have done enough research on my own to understand why they don't stand any chance of working, even as thought experiments.
There are two interesting things I note about those projects:
1) Some of the projects given on that site do not purport to be over-unity schemes, but rather are supposed to extract energy from, among other things, the sub-space "foam" proposed by string theory and the rotation of the earth.
2) Nobody presents any actual empirical test data or reproducible experimental results. Nobody claims to have actually built one, or if they have, there is some reason why it cannot be demonstrated.
I love a good conspiracy theory as much as the next guy, but in the age of the Internet, if someone really was able to build such a device word would get out and that person would be so staggeringly rich that it would make you puke.
It is a much better idea to address your own energy usage and carbon footprint by looking into proven alternatives, such as solar, geothermal, and wind power. At least there is some kind of working theory behind these, and they don't invalidate hundreds of years of reproducible scientific test results.
(People often conflate "science" and "anything technological-sounding", and people who slam real science often could not explain the scientific method if their lives depended on it.)
Torben