I'm more-or-less extremely intrigued by the Hep Message Server. It's software to abstract away the difference between different message types: In go RSS feeds, email; out come weblog posts, more email, html, or whatever. IMAP, WebDAV, Jabber are all two way.
See also: pyblosxom is a (Python) port of the tiny blosxom weblog software. Also, some musings on Hep with pyblosxom. Oh, and on a not-very-related note, Rohit Khare on generalising server to any resource over any protocol.
This is so close to where I've been thinking recently. Weblogs should indeed be thought of as a kind of flow of messages, outwards from the author, and routed and directed as necessary. Standard email filtering would be good for routing. The filesystem is good as a file store. Email is almost perfect as an extensible metadata format. Then it's a matter of putting the IM, email and www editing interfaces on top of that. Oh, and making it simple. Hm.