Tesla Motors is using Drupal for their website: http://www.teslamotors.com. Really beautiful design.
Tesla went public last year; it is the first American automaker to go public since Ford Motor's IPO more than 50 years ago.
Last month, Acquia employees (including myself) got to ride a Tesla Roadster Sport. It is a 100% electric sports car that boasts 288 horse power. The car goes from 0 to 60 mph (100 km/h) in 3.7 seconds. Not bad for a battery-powered car.
Impressive car, impressive company and impressive website. :)