Squarified treemaps #.NET

This post on CodeProject talks about squarified treemaps, which are an interesting way of visualizing the same kind of data that you might otherwise put on a pie chart. Treemaps are foreign-looking the first time you see them, but they would have some benefits over pie charts: with treemaps you don't lose all that space in the corners, and you also have a better way of viewing small segments — instead of being itty-bitty really-thin slices, they're somewhat-small squares. The article wanders far afield, and its code samples are for Avalon, so not useful for apps today; but the first quarter or so of the article contains a walkthrough on the squarified-treemap algorithm, which has plenty of illustrations and explains the algorithm quite well.

On a different note (though still on data visualization), take a look at this amazing interactive ZIP Code map. Imagine that kind of interactivity in a combo-box's dropdown.