I just got a heaping pile of (mostly undocumented) C# code and I'd like to visualize it's structure before I dive in and start refactoring. I've done this in the past (in other languages) with tools that generate call graphs.
Can you recommend a good tool for facilitating the discovery of structure in C#?
UPDATE
In addition to the tools mentioned here I've seen (through the tubes) people say that .NET Reflector and CLR Profiler have this functionality. Any experience with these?
NDepend is pretty good at this. Additionally Visual Studio 2008 Team System has a bunch of features that allow you to keep track of cyclomatic complexity but its much more basic than NDepend. (Run code analysis)