Great free resources for learning WordPress Theme Development

There are some great free resources for learning WordPress theme development out there.

This is a list of the best I have discovered...

On the WordPress Codex - WordPress Lessons the following is worth reading...  

• http://codex.wordpress.org/Blog_Design_and_Layout
• http://codex.wordpress.org/CSS
• http://codex.wordpress.org/Stepping_Into_Templates
• http://codex.wordpress.org/Stepping_Into_Template_Tags
• http://codex.wordpress.org/Templates
• http://codex.wordpress.org/Theme_Development

And not forgetting the mother of all checklists!

• http://codex.wordpress.org/Theme_Development_Checklist

Smashing Magazine have a great article on WordPress Theme Frameworks...

• http://www.smashingmagazine.com/2009/05/27/wordpress-theme-development-frameworks/

WPShout have a great series of posts on a beginners guide to WordPress theme development...

• http://wpshout.com/a-beginners-guide-to-wordpress-theme-development/

How about 8 tips for WordPress theme developers from the impressive James Whittaker?

• http://jameswhittaker.com/journal/8-top-tips-for-wordpress-theme-development/

And don't forget - Instant WordPress is also a very useful tool to consider :)