I'm looking to build/adapt a shared whiteboard app for team and educational collaboration. Draw on a board, write some text, save picture, clear board, etc. We've already got a simple chat system setup with node.js and socket.io so probably want to stay on that route.
As far as node.js technologies you would need the following
As far as rendering on the client I would recommend
Apart from that you need some kind of database, Redis, mongoDB & CouchDB are popular.
Apart from that just write it. Any other libraries you think you might need along the way can be found on the npm registry
However I can offer some package.json examples for my chat and my blog to give some inspiration as to what libraries are useful