You can find the page here http://wiki.inkscape.org/wiki/index.php/Diagramming
I invite you all to help extending the wiki page with all kind of useful information, todo's and links:
-think about requirements: how the user interface should be, ...
-how to store diagrams, is a new file format needed?
-which are the cabalities of Visio? Look for youtube-videos which explain Visio
-for users which have a copy of Visio (just like me): play with the software to learn how it solves problems
-which kind of diagrams exist and which should be supported; which types of diagram Visio support
-include a feature to build new patterns and new templates for new diagram types?
-useful lybraries and algorithms which can help in various things: alignement of elements, coloring, ...
-...and so on
I hope lots of cool ideas and features will be included into the wiki page.
First we need to know exactly WHAT we want: goals, requirements, features, ...
Than we can go on and start to IMPLEMENT these new features etc.
I am sure we can create an amazing plugin.