I wrote about BlueOxide's XML Collaborator tool yesterday. I missed part of it. The tool's core functionality is an XML registry. The XML editing tools are support structures for the registry itself.
One of the things Kevin (BlueOxide CTO) just said is that there are collaboration features built into the tool. In general, that's a good thing, but I hear more and more people talking about their tool having collaboration features (@Task was another one. I'd rather they use something like Groove's web service API to get this functionality. Of course there are a lot of tools, and integrating to all of them is difficult, but I hate to see the collaboration be liked to a tool. An enterprise needs general collaboration tools that work with multiple products, not multiple, product specific collaboration tools.