Visual Studio 2010 Ultimate supports UML class diagrams as well as sequence, component, use case, and activity diagrams. It also supports creating sequence, dependency graphs, and layer diagrams from code. Regarding your question about generating UML diagrams from code, there's a response here in the VS Architecture & Modeling tools forum: Is it possible to reverse engineer C# code into an UML Class Diagram?
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.
