OK. This is insanely cool. Check out the flickrGraph relationship map for my Flickr account. Dynamically generated flash concept map, based on the relationship data stored by Flickr.
It's also done really nicely (try dragging a person's icon around...) Kinda like ThinkMap meets FOAF meets Flickr...
Fun things that you can do with metadata (without realizing that you're playing with metadata).
UPDATE: Wouldn't it be awesome if Technorati was able to display something like this for the link cosmos for a given URL?