Libraries

* jqplot
this is an Open Source project (by Chris Leonello) plotting and charting plug-in for jQuery with numerous graph options, customizable axes, up to 9 Y axes, text axes rotation, auto trend line computation and tool-tips.
* Fusioncharts
animated and interactive graphs for web development. Fusioncharts is HTML5 and flash based, is able to work with xml.
Strong customer base (more than 17.000 customers and 330.000 users in 110 countries)
* Graphaƫl
Graphaƫl is an open source javascript library able to produce static and interactive charts.
* Emprise Javascript Charts
The name is pretty self explanatory, the main features of this product are mouse events tracking, axis scaling, auto zooming, scrolling and fully customizable
* Matplotlib
2d plotting library

http://matplotlib.sourceforge.net