This company claim they can create energy from nothing - something that violates the principle of conservation of energy

http://www.steorn.com/Default.aspx

http://en.wikipedia.org/wiki/Steorn

They are currently demoing at Spitalfields, although they are having a problem with the lighting, so it it not open to the public today

http://www.steorn.com/orbo/demo/

UPDATE:

It would appear that the demonstration has been postponed to a later date

http://news.bbc.co.uk/1/hi/technology/6283374.stm