Nodebumper is a project mainly written in JavaScript, it's free.
Flying bumping discs with Node.js and WebSockets
Multiplayer game implemented with Node.js server, WebSocket and client side canvas graphics.
Game has X players on a playing area, controlling discs with thrusters up, down, left and right. Players control thruster power to push other players out of the area.
This is not a serious project. It is meant mainly to test out server side JavaScript out of curiosity and also get some material for Bachelor's thesis.