A couple CMS-related mailing lists I've subscribed to in the past have always been boringly dominated by people gather requirements or getting reviews on CMSs; it's nice to get a little debate in there too, even if this mailing list has the same flaws as others. Is there a good place for CMS developers to discuss and debate issues? Even if we're each developing our own systems, there's a lot of interesting things to discuss I think.
Update: there's a CMS-develop list, related to the CMS list I mention above. Description: General discussions to support developers who are building their own content management system.
I've never seen a CMS list for developers, but I'd sign up for one like a shot.