Thanks for the info, guys!
Flot and flotr look nice, and since they run client-side it solves the problem of recalculating for each plot, but the images can't be generated standalone, I gather. Also, the supported graphtypes are somewhat limited.
My project is for scientific research, so I want to keep the largest set of graphtypes available.
That leaves me with matplotlib (
http://matplotlib.sourceforge.net/index.html) and ReportLab (
http://www.reportlab.org/) (thx for this one Sebastian).
I can hardly decide on one of those... matplotlib doesn't seem to install without extra effort using easy_install on Windows, though.
Does anyone know if there are any significant differences between the 2 (potential-wise), because both seem equally able to me.