I'm a bit slow on this one -- Boing Boing had it on January 9 -- but the Periodic Table of Visualization Methods is one of those things that will last a long time. And I'm sad enough to think it's fun.
What the table does is organise and illustrate approaches to visualisation from the simple (tables, pie charts etc) to the metaphorical (knowledge maps, infomurals). Each entry has a pop-up example.
There's some fascinating stuff in there, including things that are familiar in a technology context: Magic Quadrant, hype cycle, value chains, Porter's Five Forces etc. Have a broswe and you may see visualisations you have seen before but never realised they had names. You may also see visualisations you'd never visualised.
You can read about the academic background in this paper (PDF).
