The main website of the Electronic Frontier Foundation (EFF) relaunched using Drupal. The EFF is a non-profit organization with the stated purpose of being dedicated to preserving free speech rights.
According to Tim Jones, who helped with the implementation, the most interesting bit is the file-management. The EFF has thousands of PDFs spanning 15 years of legal cases to archive and organize. In the old site, these were just flat HTML links, so a big reason for the move to Drupal was to build a document management system. You can see it best on document-heavy pages like the AT&T case.