Meatball Wiki: TextVisualization is a good summary of the field with example images. Meatball calls itself an “intercommunity or metacommunity” and deals with “online culture, especially how people come together naturally in groups.” The authors, if one takes the Visualization article as an example, are building a solid knowledge wiki. Bravo.
Meatball was started by Sunir Shah who is now at the University of Toronto specializing in Knowledge Media Design.