I'll second the flot recommendation. I recently started using it on a hobby side-project (http://www.gdpinbananas.com/) and am enjoying it.
It's dead-simple and doesn't require a lot of tweaking to make the charts look decent. Check out some of the author's examples here: http://people.iola.dk/olau/flot/examples/
Comments
Try JavaScript JSXGRAPH
http://jsxgraph.uni-bayreuth.de/wiki/index.php/Hypotrochoid has a bit of a learning curve though.
Also the jQuery flot plugin http://code.google.com/p/flot/
I'll second the flot recommendation. I recently started using it on a hobby side-project (http://www.gdpinbananas.com/) and am enjoying it.
It's dead-simple and doesn't require a lot of tweaking to make the charts look decent. Check out some of the author's examples here: http://people.iola.dk/olau/flot/examples/