Here's a blog with a known life span: 2003 Denver Municipal Election. It's a running play-by-play. Makes me think that politics may be the subject that drives blogs to the social mainstream. At one point I thought it would be sports. Now I think that will come later.
Bonus link #1: Britt Blaser's Clued, which sorts examples of participatory poliblogging through the first seven theses of The Cluetrain Manifesto.