Drupal is a free and open-source content management framework written in PHP and distributed under the GNU General Public License. I started getting involved in Drupal in 2007 and back then its abilities far outreached those of many competitors. The open and transparent open source community and the way collaboration was organized attracted me to this now very large open source project.
Although my track record in the Drupal community is not as impressive as your average Drupal core developer, I do have lead many Drupal projects throughout my career. Every website created by me has been in Drupal and I've written many modules to empower small enhancements, full-fledged applications and everything in between.