CMS Watch just announced the release of an ECM Maturity Model. It was jointly developed by CMS Watch, WiPro Technologies, Smigiel Consulting Group and Hartman Communicatie and is released today under a Creative Commons "Attribution Share Alike" license.
"As Tony Byrne says, it is a V1 and the idea is to let the community participate and make it more robust."
You can download the maturity model here:
I will certainly invest some time to check it out and see if it is usable.