James Farmer has written about the whats and whys of educational blogging. This PDF covers what a blog can do (archive, syndicate, email, etc) as well as what we could use it for (virtual learning environment, news ticker-personal or course related, knowledge management for faculty, etc). There are some nice detailed examples and screenshots here.

Makes you really question what we need CMSes for in the first place. While focuses specifically on radio.weblogs this document can definitely apply to most blogs.