Google Chart API

The Google Chart API lets you dynamically generate charts with a URL string. You can embed these charts on your web page, or download the image for local or offline use. You can make a lot of things with the Google Chart API. To use this API, you should have a little HTML experience; a little patience to read the documentation; and a little persistence to keep trying if your first charts don't look as you expect them to
More information: http://code.google.com/intl/nl/apis/chart/