there is a Ruby module to use Graphviz:

http://rockit.sourceforge.net/subprojects/graphr/

Steven G.
http://linudent.sourceforge.net/

"Chris Morris" wrote..
> > I want to build a simple flowchart application.  Something like Visio,
> > but much much simpler, with an open backend that I can
> > customize/extend.  And I'd like the icon to be clickable to launch
> > another screen or flowchart.
> 
> Don't know if it meets all your needs, but have you checked out dot:
> 
> http://www.graphviz.org/
> 
> Chris
> http://clabs.org