Ask HN: Where to learn about real-time collaborative systems

One thing that I found useful was poking my head around Erlang and RabbitMQ. It's a messaging system based on Erlang. You could also check out PubSubHubbub for push notifications which is probably similar to what you're looking for.

As someone had mention, Etherpad is out there and soon Google Wave. For a Twitter clone, there's Statusnet.ca

google "remote pair programming tools" and "online whiteboard". Also look at the things people are using zeroMQ, AMQP/rabbitMQ, node.js for

examples for whiteboard:

http://www.smashingapps.com/2010/01/05/11-amazing-free-web-a...

http://vis.renci.org/jeff/2009/08/26/open-sourcing-the-big-b...

http://lifehacker.com/5503537/woobius-eye-makes-online-commu...

http://news.ycombinator.com/item?id=951621

For some hands-on experience you could try this book: "Professional XMPP Programming with JavaScript and jQuery" ISBN: 978-0-470-54071-8 Highly recommended!

Read the code to etherpad now that it's freely available.