Drupal 6 Panels Cookbook
Learning Drupal 6 Module Development
Drupal 6 Search Engine Optimization
Drupal 6 Social Networking
Beginning Drupal (Wrox Programmer to Programmer)
Leveraging Drupal: Getting Your Site Done Right (Wrox Programmer to Programmer)
Front End Drupal: Designing, Theming, Scripting
Pro Drupal Development, Second Edition
Drupal 6 Attachment Views
Drupal 6 Themes: Create new themes for your Drupal 6 site with clean layout and powerful CSS styling
