In Visual Studio 2005 and prior you could export your code to Visio and view the relationships between the objects and what methods, properties and fields it had. This was great
Visual Studio 2010 Ultimate supports UML class, sequence, component, use case, and activity diagrams. It also supports creating sequence, dependency graphs, and layer diagrams from code. Other tools include Architecture Explorer, which lets you browse and explore your solution.
For more info, see the following links:
To download the RC release, visit: Microsoft Visual Studio 2010 Ultimate RC
To see the RC documentation, see Modeling the Application.
To discuss these tools, visit the Visual Studio 2010 Architectural Discovery & Modeling Tools forum.
With VS2005 & VS2008 you have the option of designing your own modelling language (DSL) here you can choose how your model is rendered, it would be a big investment if its just to make the diagrams look a little better, but it does provide you with option to customise how the code is generated from your model.
Not quite what you're asking for but it's worth checking out some of the add-ins for .Net Reflector
E.g.
Not your answer, but related...
Codeplex's VisioAutoExt library: http://www.codeplex.com/visioautoext
Visio ActiveX component: http://www.c-sharpcorner.com/UploadFile/mgold/VisioInDotNet12032006222024PM/VisioInDotNet.aspx