Drupal 7 theme Video Tutorials
Adding some more great videos Series on this page, which will help you learn about Drupal theme, Following vidoes are sure to get you started with drupal themeing, Not only that you will also learn about what tools to use when making drupal themes.
Learn Drupal: Theme Makeover - Modifying an Existing Theme
See Below for more videos
Drupal 7: Basic Theming with Zen and CSS
The following series of 6 videos will show you how to create a drupal theme from HTML
Following is a series by Lullabot. The first video I have embedded down below. For other videos you will have to register on the website to view it.