Freebie from Microsoft. Ian Morris has a demo page setup for the Chart Web Part.
The Chart Web Part can be used to generate charts in the Windows SharePoint Services environment. The Web Part supports data coming from XML files and Web Part Connections, and it generates charts as either an server-side images or as VML. This Web Part works great in complementing the Data View Web Part to provide a powerful data reporting story.
Download the file and save it to your computer. Unzip the file and consult the instructions included with the Web Part. Although it was designed for SPS 2003, it works fine on MOSS as demonstrated by Ian.
Via IAN Morris