"Our first Drupal 6 beta version was released just over a month ago, so given the large number of usability improvements and bug fixes that we've added since then, we're proud to announce the release of the second beta version of Drupal 6.x for your testing. This beta version includes all the latest security bug fixes as released in Drupal 5.3 and 4.7.8."
http://drupal.org/drupal-6.0-beta2