Anyone with an interest in the history of computing will know that the first mechanical computer was invented by one Charles Babbage, British mathematician and visionary. If you happen to be in the vicinity of the Science Museum in London you can even see a working difference engine, something Babbage never did in his lifetime as he died before a prototype could be completed.
Amazingly, according to this story a number of scientists in the US are now working once more on mechanical computers. Fair play, they are likely to weigh less then the two ton steampunk Babbage creation, a lot less in fact. These computers are comprised of nanomechanical parts, meaning the entire computer could actually be smaller in size than a silicon transistor of today.
The Defense Advanced Research Projects Agency, a player in the development of the original Internet, is funding the research in order to create tough computing devices which could survive the harshest of environments. Environments such as the insides of weaponry for example.
I rather like the description of the transistor created from nanomechanical pillars at the University of Wisconsin which are made from silicon oxide tipped with gold, and measuring just 30 nanometres across. Still huge according to the man behind the development, who claims they could make one a third as big if they wanted to.