I would like to see if I can port one of the sites I maintain to WordPress so I can turn it over to the owner. Here is a collection of links to perhaps useful sites.
http://codex.wordpress.org/Theme_Development
http://codex.wordpress.org/Using_Themes
http://blog.circlesixdesign.com/2006/12/25/wordpress-theme-development-workflow-for-osx/
http://www.cre8d-design.com/blog/2007/01/01/useful-resources-for-creating-a-wordpress-theme/
http://lorelle.wordpress.com/2005/08/22/designing-a-wordpress-theme-building-a-sandbox/