Drats, I missed my drupal.org 10th birthday!
I was actually using Drupal before drupal.org existed, and my http://dirtbike.ws website - currently re-branding as http://mydirtbike.com - would be amongst the longest running Drupal based sites there is.
I've seen Drupal go through fantastic growth through the years, and the future looks brighter every day, with new Drupal companies appearing, new conferences, camps and meet-ups, the Drupal ecosystem looks to be very healthy.
Keep up the good work Dries & co.
Drupal has been very helpful to me over the years, and I look forward to a fantastic next 10 years of Drupal usage, coding and conferences ;-)