> 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