Probably just about everyone has this book already, but if you're interested in a fine book on Drupal 5, Apress is offering the Pro Drupal Development ebook for only $10 through their Daily Deal.
I'm not affiliated with the authors, publisher, or anything like that. I just keep an eye on that page, and wanted to pass this along for people who might not have the book yet.
The folks over at CMS Critic have published an extensive and interesting interview with Dries Buytaert, Drupal founder. The interview is part one of a two part series on Drupal, Acquia and Mollom.
Drupal 6.6 and Drupal 5.12, maintenance releases fixing problems reported using the bug tracking system, as well as critical security vulnerabilities, are now available for download.
Upgrading your existing Drupal 5 and 6 sites is strongly recommended. There are no new features in these releases. For more information about the Drupal 6.x release series, consult the Drupal 6.0 release announcement, more information on the 5.x releases can be found in Drupal 5.0 release announcement.