Try: http://www.amcharts.com/pie/ http://www.solutoire.com/plotr http://www.liquidx.net/plotkit/

Great Flash charts: http://www.maani.us/xml_charts/

GD::Graph is great and quite sophisticated: http://search.cpan.org/~bwarfield/GDGraph-1.44/Graph.pm

Chart::Strip is neat: http://search.cpan.org/~jaw/Chart-Strip-1.05/Strip.pm

RRDTool is amazingly powerful for time-lapse data: http://oss.oetiker.ch/rrdtool/

I am using XML/SWF Charts on my site. (http://www.maani.us/xml_charts/) You can see an example here: http://www.carhuntr.com/prices-Chevrolet-Suburban.html

It is easy to work with, and I have tested it using browsershots. Displays correctly in almost all browsers. My only concern is the load-time. So far it does not seem too bad.

http://www.adobe.com/products/flex/charting/ (it is affordable, but not free)

I've been really impressed with flex charting and if the 300 bucks isn't too much for ya, I would recommend it. Google finance is a good example of it's power and integration ability with javascript.

FusionCharts is good, well documented, and damn cheap (but not free). They do offer a fully functional trial version-- it just has a big "demo" label on resulting flash graphs.

We use it for http://www.rescuetime.com....

Here's the chart gallery for FusionCharts: http://www.fusioncharts.com/Gallery.asp?gMenuItemId=3

The http://www.dojotoolkit.org JS toolkit has a pretty good charting library, and the developers are quite responsive.