Not only an interesting discussion of the possibilities for the future of WP themes, but also ends up including some very helpful links as well to theme development resources.
I love it when other people have done the hard work of searching through WordPress plugins and then save ME the work by sharing their knowledge!
The title pretty much explains it.
A 16 part, step-by-step guide to building a WordPress Theme.
A simple, customizeable WP theme. Also has interesting discussion about web development/design including typography.