Together with Morten, one of the best Drupal themers, I will give an introduction in Theming for Drupal-6. So, if you aer interested in theming for Drupal in general, or Drupal6 in specifics, make sure you pop in at the Drupal-developers room.
About the author: Bèr Kessels is an experienced webdeveloper with a great passion for technology and Open Source. A golden combination to implement that technology in a good and efficient way. Follow @berkes on Twitter. Or read more about Bèr.