Two Column Themes
ClearPixels is a widget-ready theme fully compatible with WordPress 2.5. Native Gravatar (2.5+) and tagging support. Also has an optional "sitewide announcement" configurable via a theme options page.
iPhonized is a two column widget-ready theme. The theme supports custom fields. The titles and comment counts are surrounded by rounded corners. The comments are embedded inside speech boxes.
Spotlight is a free WordPress theme with 3 widgetized areas in the sidebar (top, left, right) along with native Gravatar (2.5+) and tag support.
Three Column Themes
Mag Essentials is three column widget-ready theme. The theme has a wide sidebar and has space for banner ad integration. The theme has a magazine style Design.
Pundit is a three column widget-ready theme designed to focus on the writing. Perfect for news or political blogs or for anyone who anyone who wants to keep it simple.
WP Platinum is a 3 column widget-ready theme specifically created for Firefox. The theme has a featured article section.