An interesting article on visualization of 'the net ... Under socialnetworking, LastFM is mentioned a couple of times as is youtube, but fidgt is just way off of the map. ;-)
I remember seeing a LC project around 1998 or so (tied to American Memory? funny, I can't remember!) which visually mapped parts of the collections, so that you could see the relationships between items. I'm not sure what happened to that.
Anyhow, here is the article intro :
The Best Tools for Visualization
Visualization is a technique to graphically represent sets of data. When data is large or abstract, visualization can help make the data easier to read or understand. There are visualization tools for search, music, networks, online communities, and almost anything else you can think of. Whether you want a desktop application or a web-based tool, there are many specific tools are available on the web that let you visualize all kinds of data.
Article in entirety