David Weinberger pointed out some Cool visualizations last week, and I just had the chance to take a look.
Of course, Bestiario use the visualization tools on their home page instead of the traditional corporate website.
This image is a screen grab of their delicious browser. The basic setup isn't too unusual for a network visualization. You can spin the network to explore the links in more detail. The circles are specific web links, and the rectangular words are tags. Interestingly, the tags give you just enough to understand what the selected topic is about, particularly if the taggers have been busy (or automated). With a link to a biography in Wikipedia, the network shows birth date and birth location along with other highlights. The particularly new thing (to me) is the list of links on the right side.
Unfortunately, I don't see a way to point to your own materials and play with those.