Hi, I'm looking to build an interactive web-based org chart for a large organization. I somewhat like the interface at ancestry.com where you can hover over people and pan/zoom around and click on different nodes to make them the root.

Ideally, I'd like it if people could belong to multiple organizational entities like committees, working groups, etc. In other words the API should support graphs in general, not just trees.

I'd like to be able to visually explode each organizational substructure into substituents by clicking on it, with a nice animation of the employees ballooning or spilling out so you can really interactively drill down through the organization.

I found http://code.google.com/apis/visualization/documentation/gallery/orgchart.html but it looks a bit rudimentary.

I know there are desktop tools like OrgPlus and Visio that can build static charts but I'm really looking for a free, web-based API with open standards-based output like SVG or HTML5 Canvas elements rather than Flash or some proprietary output. Something I can embed into a custom web application and style myself. Something interactive.