If you use Visual Studio, the 2010 Ultimate release lets you generate sequence diagrams and dependency graphs. However, the release currently supports only .NET application projects.
The team has gotten lots of interest in supporting C++ in a future release, so you might want stay tuned. In the meantime, you can post in the VS 2010 Architectural Discovery & Modeling Tools forum at http://social.msdn.microsoft.com/Forums/en-US/vsarch/threads to request an update. I know the product team loves hearing customer feedback about the tools.
In the meantime, you can learn more about creating sequence diagrams and dependency diagrams from .NET code in the following topics:
How to: Find Code Using Architecture Explorer: http://msdn.microsoft.com/en-us/library/dd409431%28VS.100%29.aspx
How to: Generate Graph Documents from Code: http://msdn.microsoft.com/en-us/library/dd409453%28VS.100%29.aspx#SeeSpecificSource
How to: Explore Code with Sequence Diagrams: http://msdn.microsoft.com/en-us/library/ee317485%28VS.100%29.aspx
To try the RC release and provide feedback, download it at http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=457bab91-5eb2-4b36-b0f4-d6f34683c62a