Mozilla Thunderbird using Drupal
Mozilla launched spreadthunderbird.com this week. Spread Thunderbird is the volunteer-run Thunderbird advocacy site where community marketing activities are organized to raise awareness and to promote the adoption of Thunderbird, Mozilla's Open Source e-mail application. The Spread Thunderbird site is powered by Drupal and uses the Acquia Marina theme. They are also using Mollom to protect their site against spam. Hopefully the site will be as big a success as spreadfirefox.com, which has been a Drupal site for many years.
— Dries Buytaert