Inspired by aharef's html visualizer here's another del.icio.us visualization, but in this case, instead of mapping tags it explores the relationships between del.icio.us users. This network explorer is written in processing and uses force directed graph visualization. The edges between the nodes act like springs. New nodes start from a random position and run to convergence.
You can input your own del.icio.us username and see your network of acquaintances build in front of your eyes, assuming of course you've been using the network feature in del.icio.us. For other projects featured in VC, that aim at visualizing the del.icio.us tagging system, you can see more here.