WordPress celebrates its seventh birthday, today 27 May, 2010. WordPress was first released on 27 May, 2003 by Matt Mullenweg.
Original announcement: http://wordpress.org/development/2003/05/wordpress-now-available/
WordPress has evolved into a great CMS capable of much more than just running blogs and will soon reach another milestone with the 3.0 release.
Happy birthday WordPress, Roll on the next 7 years.