This site is a Drupal site. I started with Drupal 4.6.8 and recently upgraded to Drupal 6. I find the best way to learn Drupal is to experiment with your own sites. Of course, using a sandbox (development area) is highly recommended for those large design adventures.
I have been keeping notes on the upgrade from D4 to D6. The images show the before and after. Not much has changed yet. The new theme is still in production. I wanted to get the architecture and content online and then focus on the visual aspects of design.
Update 7/5/09: Other projects are keeping me busy so I am considering this phase of my upgrade done. The content on this site will continue to change as it is my blog space.