Shakeoff is a game where two players attempt to handshake as close to their own side as possible. There's a 10-second time limit, though, so you have to be quick.
Because it's the hot new thing, actual gameplay happens in the URL bar.
On the backend, shakeoff is based on Coffeescript, Node.js and the excellent Socket.io. On the frontend, jQuery and the HTML5 history API.