Take a look at Programmers.SE (and especially it's FAQ):
Programmers — Stack Exchange is a site for professional programmers who are interested in getting expert answers on conceptual questions about software development. If you have a question about...
- development methodologies
- quality assurance
...then you're in the right place to ask your question!
But be careful; CMMI is a general QA process, not specific to programming. Asking questions on how to apply it to a software development process might well still be on topic though.
The rule of thumb for choosing between Programmers and SO is: Are you at the whiteboard? Use Programmers. Design done but stuck coding? Go to Stack Overflow.