It's pretty solid list, covering a spectrum of informative sites. I also appreciate that they've taken care to keep things vendor agnostic, focusing more on sites that deliver broad-based information and news rather than a hocking a specific product. I will say, however, that I would suggest a few additions.
FierceContentManagement was obviously too humble to include themselves on their own list, but they're one of the better content management sites out there. I'd also include the fairly new ECMHUB.com, which doesn't have much in terms of original content, but does a great job of consolidating content from across the web. I also recommend the always insightful Column Two, as there's a gem or two in just about every article they publish.
Not exclusively content management sites but close enough to mention are Smashing Magazine and ReadWriteWeb, which both are more focused on design and publishing. But when they do discuss content management, they cover it with style.
Any favorites missing from FierceContentManagement's original list or the sites I've mentioned? Speak up in the comments.