The flagship site of Oxfam International, http://oxfam.org, is using Drupal. Oxfam is also using Mollom to protect their blogs from comment spam. Oxfam International is a confederation of organizations actively working in more than 100 countries to find lasting solutions to poverty and injustice. I've always believed that Oxfam was big on Plone, so I wonder why they decided to go with Drupal instead? Regardless, it's great to see that Drupal adoption continues to grow in the non-profit sector.
— Dries Buytaert