By no means comprehensive, and currently listed in random order without categories to guide you (bad WCM girl!):
CMS Watch evaluates content-oriented technologies and develops comparison reports.
Occam’s Razor is the home of Avinash Kaushik, whose thoughts on web analytics are often in plain English, usually interesting, and almost always immediately useful.
The Content Wrangler publishes excellent real-world articles for content management professionals.
Usability Professionals Association–a professional organization for people in charge of making web content DO something.
Click Wisdom is a blog about using your website for effective marketing.
Web Style Guide, for those of us sick and tired of capitalizing web and hyphenating email. (second edition)
Adaptive Path blog is written by some of the field’s most reliable thought leaders, in my humble opinion.
EContent keeps up on digital strategies and resources so you don’t have to! Boring, but useful.