I've been coming up with examples of who is using Drupal. I usually just point people to my growing list of Delicious links. There's also summaries available from BuiltWith, which rates Drupal the most popular of their reviewed CMS's. However, I thought that this was probably a more timely way to organize it. This is pulling information out of Delicious' RSS feeds to allow me to post new links that other people find interesting.
There are a number of musicians who web presence is delivered by Drupal. Bob Dylan, Ozzy Ozborne, Moby and Avril Lavigne are prominent examples, but also: