redesign.drupal.org is what we will be launching when ready. User/pass: drupal/drupal.
Theme changes are deployed within 2 minutes. Module changes are pulled from CVS by BZR admins. The database is rebuilt from a fresh copy of Drupal.org every day. This is meant to emphasize that changes to code should be committed to CVS modules and the main copy of the theme. And database changes need to be done on Drupal.org, or automated in drupalorg_update_65xx().
The redesign.drupal.org database is provided for development. Private data is scrubbed, including password hashes. Log in with 'drupal[username]'.