The Microsoft Office Interactive Developer Map is a Windows Presentation Foundation (WPF) application that helps developers visualize the different programs, servers, services, and tools that will help them build solutions. It allows them to drill down to each product and technology and learn about new features, objects, Web services, namespaces, and schemas required to extend Microsoft Office and build custom Office Business Applications (OBAs).
This is such a useful tool. I wish we (Microsoft) had it too for the rest of the server-side platform stack not part of the Office System! Go get it here.