I am a huge fan of Vagrant ( http://vagrantup.com ) which is virtualized development environments, package-able. Works with chef and virtualbox. I don't know if I can state just how game changing this is for me.

DocumentCloud really dropped some bombs this year. backbone.js, underscore.js are really great.

Socket.io saved my ass. I promised some big clients that I could make websockets driven apps for the iPad and then apple pulled websockets support without saying anything. So I was able to get socket.io for the win.