If you are interested, here is the same. If my wife permits me to spend a couple of hours in front of my box this sunday, I'll do some quick refactoring to clean up the code a bit more- and may publish the source with another detailed article. In this Video, you may see I'm logging in from two different browsers, to do some dirty drawing that gets pumped to the other user.
I think recently there is lot of excitement about Google Wave, mainly because of it's ability to share information between various users real time, over HTTP. Real time information sharing is not new - but note that point - " over HTTP" - which makes it accessible to a wider audience.
(Some time back, to understand how Wave works, I even made a small Wave Robot based on Jon Skeet's API - Read about the same here if you missed it.)
Long point made short - If you are in MS camp, and if you are looking forward to develop RIA apps that can seamlessly share information between users real time, you may have a look at Silverlight + WCF Polling Duplex. I still need to explore scaling and performance related aspects