Plotr is an excellent charting library built in prototype.  It outputs to a Canvas / SVG drawing object. (IE 6+ Support is powered by the ExplorerCanvas library).

It currently supports:

• Bar Charts
• Line Charts
• Pie Charts
• Chart Legends

All in all, it’s an excellent lightweight library for adding basic data visualization capabilities to your app.  More importantly, the chart’s it generates are simply stunning, complete with drop shadows, white outlines, & well designed default color schemes.

Check it out online here:

http://solutoire.com/plotr/

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