Every now and then, I remember about the great search application called Kartoo. It's a flash UI on top of a bunch of search engines, and does some really interesting things with the aggregated search results. The coolest (and most visible) thing is the "concept map" view of search results - and this display doubles as an on-the-fly social network diagram.
For example, I just did a quick ego search (don't laugh - you do it too. fess up!) for "darcynorman.net" to see what kind of diagram came up. I was surprised by how on the mark it is. The diagram is a good starting point (although far from comprehensive) for getting an idea about what interesting bits I published (since only those will be linked to by others), and you get a rough idea of my immediate social network. The display is paged, which is unfortunate and counterintuitive (since you can zoom and pan the diagram, and pagination only makes sense for text lists...). Here's a screenshot of the second "page" of results mapped out: