Of ImageMagick Perl and ASE's ChartDirector for Perl (and perlchartdir it provides), which is for pay... but relatively cheap if you are only using it in-house to produce charts and such. IOW, not redistributing it. Even then its not huge money.
Its what we use for our Dashboard Application and RealTime Charts and Graphs.
They come out real purty. Works well enough to look very good on the iPhone and other Mobile devices, as well as regular browsers.
While looking for an example... I stumbled across this. Seems to explain in the code what is needed... we dynamically provide the data (of course) and its just plain works.
Here is the Product page:
Here is a Forum, don't know how old, active or anything... its looks to have been active at one time and has a lot of good chewy details in it.