The whole field of fluidics is fascinating, including entire digital logic families that operate at kHz rates with no moving parts and no electricity, just air. I wrote a kragen-tol post about this in 2002 http://lists.canonical.org/pipermail/kragen-tol/2002-April/0..., when Air Logic still sold actual logic gates that ran on air, but since then Google Books has archived this June 1967 Popular Mechanics article, "How They've Taught a Stream of Air to Think": http://books.google.com.ar/books?id=jSEDAAAAMBAJ&pg=PA11..., and of course fluidics has become practically very important for on-chip microarrays. There's also a Wikipedia article now: http://en.wikipedia.org/wiki/Fluidics