First Evil journal
Suddenly the fictional-blog thing seems to be coming into vogue.
If you've been watching this season of Buffy, you might enjoy (Warning: Major spoilers for recent episodes of Buffy and Angel if you follow this link!) the First Evil's LiveJournal, which (from what I read of it) is somewhat entertaining in itself (in somewhat the same vein as Sauron's Very Secret Diary) and very entertaining if you read the comments, many of which consist of Buffy and Dawn sniping at each other. (B and D have their own LJs that you can get to by following the links, of course.)
Meanwhile, Kevin Raybould of Lean Left has started a blog for a fictional character of his own creation; apparently it's going to be an ongoing story. I haven't had a chance to read it yet.