I found Indexed through Freakonomics. It demonstrates the principle to “invest a little, learn a lot.”
Jessica Hagy makes amusing little diagrams. They look like they’re hand-drawn on index cards, but I’m not sure.
Indexed is planned to be released as a book in February 2008.
She says: “This site is a little project that lets me make fun of some things and sense of others. I use it to think a little more relationally without resorting to doing actual math.”