Kyle Scholz has developed code to represent Force Directed Graphs in Javascript, and you can interact with the nodes. We’re talking mathematical directed graphs here – you might know them as networks.
Basically, there’s a bunch of nodes and they settle themselves into a stable state minimizing tension between them – the graphs balance themselves out, and you can see it happening – it’s animated. And interactive – you can grab a node and move it around. It is ubercool.
Downside is that it sucks huge CPU.