Drupal 6.5 and Drupal 5.11 were released yesterday. These new versions of Drupal are maintenance releases fixing problems reported using the bug tracking system, as well as critical security vulnerabilities. If you take a look at the release notes, you'll find that Drupal's core developers and security teams have been hard at work improving this open source content management system. With all the hard work done for you, it only makes sense to upgrade your Drupal site today (yes, we're running Drupal 6.5).
Details and download links can be found at Drupal.org.