Graphs and charts for the web

Anyone have any nifty methods for creating nice looking charts and graphs dynamically on the web?

I'm currently using .png files created in Photoshop that I stretch via the width element to the desired size based on a variable.

I have some data I'd like to plot using a line graph but I haven't liked what I saw so far. Google has an option but they have some weird size restrictions.

I also found this http://www.r-project.org which seems a bit much for what I want but I may end up having a back end script that generates an image from a data set.

I'm hoping people much smarter than I have a better idea.