Starkers is a bare-bones WordPress theme created to act as a starting point for the theme designer. Free of all presentational elements and non-semantic markup, Starkers is the perfect ‘blank slate’ for your projects, as it’s a stripped-back version of the ‘Default’ theme that ships with WordPress.

All non-semantic, presentational class names (e.g: class=“center”, class=“alignleft”) have been removed; all non-semantic, presentational HTML elements (e.g: <hr />, <br />) have been removed; all unnecessary elements have been removed (e.g: <div class=“entry”> disappears entirely and <h3 class=“comments”> simply becomes <h3>).

Elements have been converted where necessary (e.g: <small> becomes <p>) and some IDs have been kept intact (such as <h3 id=“respond”>) to preserve functionality.

Best of all:  Starkers is free and fully GPL-licensed, so you can use it for whatever you like, even your commercial projects.

Pricing: Free
Requirements: Wordpress 2.8.1
Source: http://elliotjaystocks.com/starkers/