Google Chart API

Google Chart API allows you to dynamically create charts by just passing parameters to an URL, it's pretty amazing. You can generate all kinds of charts, check it out...

http://code.google.com/apis/chart/types.html

Check this simple example:
http://chart.apis.google.com/chart?cht=p3&chd=t:60,40&chs=250x100&chl=Hello|World