Mahablog has two excellent posts analyzing (and linking to other good analyses) of the changes the Left and Right blogosphere experienced over the last several years and explains why the Right blogs were more powerful in the beginning and why the Left is much more effective today:
Under the Radar
Old Dogs
More like this
Thanks to Avedon, Mike,
Long-time observers of the progressive blogopshere are likely aware of Barbara O' Brien and her blogging at The Mahablog, Crooks and Liars,
Here's some Sunday reading for you: