Mike from work pointed me to EpiSpider, which does dynamic graphs and uses in part an in-browser library for faceted browsing called Exhibit, from the SIMILE project. This project also has a beautiful Timeplot library, again in-browser.

The basic approach here is minimalist: all a site developer needs is a place to host Web pages, some of which are data files. No database, no content management system. Still, those have their places too, and I can already see how to make great use of Django features as well as Exhibit and Timeplot features, and I know databases. To tie these together, one just needs a bit of AJAX code to call a server-side process to pull the appropriate subset of data from the database in JSON or other simple format, and I know that exists too.

I had been ready to try generation of static chart images in order to save time -- that was why I was trying to use R (also the data import, manipulation, analysis and export features could be useful). But ultimately good online charts need features like mousing over to see point values, scrolling, and zooming; static charts can't provide that but in-browser canvas code like that used in Timeplot can.

Sample here.

Update: removed annoying iframe