Other related projects you may be interested in.
Sparklines a PHP library that makes tiny graphs which are ideal for placing in titles or text.
Graph geeks bible, less is more. Effective visual communication of data.
http://en.wikipedia.org/wiki/Pareto_chart, combination of bar and line chart showing the 80:20 rule.
The Long Tail.
I find choosing colours that compliment each other rather daunting. Try this: eye pleasing colours.
An open source PHP graphing system: graidle.
Flash guages: SWFgauges 1.0.
five3d looks interesting.
How to draw nice charts: Edward Tufte,
The Visual Display of Quantitative Information