This is the Democratica theme that is a part of the CivicSpace distribution of Drupal.
The author is Chris Messina (FactoryJoe), who also brought us the SpreadFireFox theme.
Note: this theme requires the PHPTemplate theme engine.
It has similar features to that theme, and some limitations too (e.g. the white space issue caused by the 'clear' in the misc/drupal.css file. Remove the clears from that file or delete it altogether).