Defcon!!!
Defcon is a stopwatch running on Node.js, Express.js, and Socket.io. It is intended to be a good starting point if you're just learning to use web sockets. It currently uses xhr-polling so it is compatible with Heroku.
Who's it for?
I originally wrote Defcon over four blog posts introducing Socket.io and deploying to Heroku. Please checkout the posts on my site, robdodson.me