Not sure if this will help, but here goes:
1)
http://www.cnet.com/topic-software/sirius.html
they offer a list of downloads for different PHP programs and applets that can display different kinds of graphs. I think they are all free to download, but I am not sure.
2)
http://www.jpowered.com/graph_chart_...h-servlets.htm
This page looks scary to me, but maybe you're more programming savvy than I am.
3) Have you looked to see if you can integrate documents from
http://www.openoffice.org into your website?
4) Although not practical, especially if you want the graphs to appear on demand, you can always save an image of the graph and post it on the page as an image. I have a feeling you want it to be more dynamic.
I hope you'll find what you're looking for in one of the options above. If I come across another one, I will post it on here. Let us know!
Sherif