Google Chart Tools

Google Chart Tools provide a perfect way to visualize data on your website. From simple line charts to complex hierarchical tree maps, the chart galley provides a large number of well-designed chart types. Populating your data is easy using the provided client- and server-side tools.

http://code.google.com/apis/chart/interactive/docs/index.html

http://net.tutsplus.com/tutorials/other/easy-graphs-with-google-chart-tools/