Second Life using Drupal
With all the craziness surrounding Second Life, it is probably worth pointing out that Linden Lab (creators of Second Life) uses Drupal for http://lindenlab.com and http://teen.secondlife.com.
And from the looks, they use Wordpress for their official Second Life blog. Great to see that start-ups can excel (and be profitable faster) with the help of FOSS.
— Dries Buytaert