Right now I evuluating a new software called NDepend. NDepend is installad as a Visual Studio plugin. I havn't use it much yet, but I have already found a feature that I like a lot. It is the dependency graph. The graph show how assemblies is related to other assemblies in your Visual Studio solution and to external assemblies. You can easily show information about an assembly buy hover over an assembly in the graph.
With Visual Studio Ultimate you can generate dependency graphs out of the box. But I think that the tool for dependency graphs in NDepend gives me a much better overview than the tool in Visual Studio Ultimate and it much easier to use.
When I have evulated it more I will write a full review of the software.