I am now a Lynda.com author. My first video title "Drupal: Creating and Editing Custom Themes" is out now and is an online exclusive. The course teaches the basics of Drupal themes - what they are, how to control them, and how to build your own theme from scratch. The course is a little over 4 hours long, so you should be able to complete the course in a day or less.
Watch how to theme Drupal online now at http://tinyurl.com/theme-drupal