Computers
I program, and I know a few languages, including C++, several varieties of BASIC, LISP, Haskell, and Z80 assembly language. But I really don't have much else to say here, except that I do the USACO, a programming competition run over the internet.
And now I've written a decent (I hope) tuturial on how to use Cluster, a "supercomputer" made up of 16 desktop computers.