Microsoft "Oslo" Web Page
Now that PDC is in full swing, the Oslo Developer Center has been published. It contains a lot of great information about the whole Oslo platform - the Repository, the M modeling language, and Quadrant. Quadrant is the specific piece that I work on so I've spent most of my time reading through the info they posted about it. Unfortunately there are no Quadrant bits for you to download, but there is a lot of good information.
The tools component within "Oslo" creates a layer where the multiple roles (analyst, architect, developer, IT Manager, etc) within an organization can visually share and collaborate on models, using the specific view of the model suited to their needs. Models can be edited either using the new modeling tools, or can be exposed through the existing familiar tools that the end-user already knows (e.g. Visual Studio, BizTalk, SharePoint, Visio, etc).