A new free and open project to implement a web based social network visualization front end is available on Codeplex: the “Information Connections Engine (ICE) is a Silverlight based framework that allows .net developers to easily visualize any type of information, as well as links between information in a user friendly and entertaining way.”
The video is a hoot (but seems to go blank after about 4 minutes). This looks like a great start towards an interactive web canvas for network graphs.