I am always facinated by interpersonnal networks and the ability to identify relationships between the people you know. LinkedIn, the work focused social-networking site, has unveiled InMaps, a tool that maps your entire social network, color coded by associations.
I am not exactly sure about how the color coding is derived, but I tried to take a guess at the relationships on mine. Various affiliations between the contacts are color coded and the bigger a node is, the more strongly connected a person is in a particular network.
As I was poking around to figure out why people were color coded they way they were it made me think about people I'd not talked to in years. You can zoom in or out as each node is labeled on your own plot.
Here is a picture of mine