Visualization tools: 40 free charts, diagrams & flowcharts
Free useful resources for presenting data in user-friendly formats. Brief descriptions and links at: Smashing Apps’ 40 Useful and Free Visualization Libraries: Charts, Diagrams and Flowcharts -Free and Useful Online Resources for Designers and Developers
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That article missed IBM’s Many Eyes:
http://www-958.ibm.com/software/analytics/manyeyes/