The first real nano-computer has been built on a single carbon fibre according to the BBC science and technology site – http://news.bbc.co.uk/1/hi/sci/tech/4839088.stm.  The circuit is made of palladium and aluminium and is 18 millionths of a metre across.

This is a proof of concept rather than a commercial model, but still shows impressive promise for the future of tech.