CSS desk
Write HTML & CSS live in the browser
http://cssdesk.com/

30 Days to Learn CSS & HTML
http://learncss.tutsplus.com/

Wordpress tutorials
http://wp.tutsplus.com/

Underscores Starter theme
http://underscores.me/

Wordpress Template structure
http://codex.wordpress.org/Template_Hierarchy

Demo site
http://wp.timsnyder.me/