March 3rd, 2010
Drupal 6.16 and 5.22, maintenance releases which fix issues reported through the bug tracking system, as well as security vulnerabilities, are now available for download. Drupal 6.16 also fixes other smaller issues.
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 the Drupal 5.0 release announcement. Drupal 5 will no longer be maintained when Drupal 7 is released. Upgrading to Drupal 6 is recommended.