JS/Linux
If you are running Google Chrome 11 or Firefox 4 or later and you know how to find your way through a Unix console OS, here’s something you might want to check out: it’s a Javascript PC emulator running a custom (patched) build of the Linux kernel 2.6.20. Directly. On. Your browser. With Javascript.
And it’s made by the same guy who wrote QEMU!
Javascript.