For drawing graphs in TiddlyWiki, there are some graphics libs like
jsx and raphael available as plugin.
But drawing an actual graph is not that easy.
I made a start using the d3.js lib for data visualisation and the
first graph type I made is a horizontal graph or pareto graph. The
d3.js can be found here:
http://mbostock.github.com/d3
To draw a pareto I made a plugin that is available at
http://d3tw.tiddlyspot.com
keep in mind that it is still very experimental.
Make sure to have a backup of your important data.
Any comments are welcome, Okido