graph_libraries_for_rails

jQuery Visualize Plugin: Accessible Charts & Graphs from Table Elements using HTML 5 Canvas
http://www.filamentgroup.com/lab/jquery_visualize_plugin_accessible_charts_graphs_from_tables_html5_canvas/

Bluff is a JavaScript port of the Gruff graphing library  for Ruby.
http://bluff.jcoglan.com/

Open Flash Chart II Plugin for Ruby on Rails - Graphs (we have used this before for interactive charts)
http://pullmonkey.com/projects/open_flash_chart2/

Interactive JS charts for your website (free for personal use):
http://www.highcharts.com/

amCharts: Sexy charts in less than 5 minutes
http://railsontherun.com/2007/10/4/sexy-charts-in-less-than-5-minutes

JS charts (free for personal use)
http://www.jscharts.com/home

Gruff
http://nubyonrails.com/pages/gruff

Google charts
http://code.google.com/p/gchartrb/
http://googlecharts.rubyforge.org/

Flot is a pure Javascript plotting library for jQuery. It produces graphical plots of arbitrary datasets on-the-fly client-side. (sent by @eparreno)
http://code.google.com/p/flot/

A list of 20 JS chart libraries (via @Joel_Hughes on twitter)
http://sixrevisions.com/javascript/20-fresh-javascript-data-visualization-libraries/

14 Javascript Resources And Plugins For Creating A Stylish Chart (via @josevalim)
http://www.webdesignbooth.com/14-javascript-resources-and-plugins-for-creating-a-stylish-chart/

Raphaël is a small JavaScript library that should simplify your work with vector graphics on the web. If you want to create your own specific chart or image crop and rotate widget, for example, you can achieve it simply and easily with this library. (via @josevalim)
http://g.raphaeljs.com/
http://raphaeljs.com/

13 Useful JavaScript Solutions for Charts and Graphs (via @jorgegorka @smashingmag)
http://webdesignledger.com/resources/13-useful-javascript-solutions-for-charts-and-graphs