The Google Chart API returns a PNG-format image in response to a URL. Several types of image can be generated: line, bar, and pie charts for example. For each image type you can specify attributes such as size, colors, and labels. And best of all its absolutely free!
You can include a Chart API image in a webpage by embedding a URL within an
<img> tag. When the webpage is displayed in a browser the Chart API renders the image within the page.