At one of my jobs, I'm working with d3.js to develop visualizations of scholarly data, such as article citations and co-authorships. I'm not ready to show off that work yet, but I got a bee in my bonnet to make some useless/pretty pictures. The main inspiration was gmunk's work on TRON - SO NICE. My work obviously does not compare, but it's been fun to try things with a playful attitude.

Here is one

Here is another

Incidentally, Mike Bostock's is both handy and a cute use of gists.

Finally, the best d3 visualization I've seen is this globe with overlaid weather data. Really amazing!