I’ve just come across a new site called Themes Wiki which might be of interest and help to those of you trying to modify your theme, or assist you when creating you own WordPress theme. ThemesWiki.org provides a range of free guides and tutorials for designing themes for WordPress as well as a wide range of other Content Management Systems and related software such as Joomla, Drupal, PHP-Nuke, and phpBB etc.
The site provides some useful information about configuring WordPress themes as well as developing WordPress themes, and being an open Wiki also allows you to contribute and add you own content. Check it out at ThemeWiki.org.