Ask HN: Collaborative Diagramming

Does anyone know of a collaborative diagramming framework/software.

I can't seem to find anything out there.

Essentially I envision a visio/mind map style web page that allows for a modular wiki-style article entry. You could have each node/child have associated web pages, images, documents, text snippets or sub layers of diagrams.

Does anyone know of something like this that exists? I think it'd be great for collaboration!