Capability Maturity Model Integration - Wikipedia
Actually a good summary of the history and current version.
CMMI FAQ - brutally honest, totally hip, no nonsense answers (a public service of Entinex)
Just search for Agile in this incredibly long FAQ. This URL actually puts you at one of those Agile and CMMI explanations, but there are more if you search.
(11) Agile CMMI | Groups | LinkedIn
Use the LinkedIn group to find people you trust to talk CMMI and Agile. Or ask Mark Kilby.