Gicio:
The Microsoft Patterns and Practices team is in charge of developmeing the Software Development Life Cycle for Microsoft and creating recommendations for partner developers. Check out their page at
http://www.microsoft.com/resources/practices/
Other than that, XP isn't getting too much of a foothold in most of the companies that I have worked with or spoken to here in the Midwest anyway. Most everyone uses a Use Case based design model, then a traditional waterfall style development process for large process, or a RAD circle on small projects.
Bill Sempf
Effective Visual Studio .NET