davidbisset, 
More #WP20 perspective:
2003 - WP born.
2004 - #bbPress
2005 - #automattic
2006 - ModernTribe
2007 - Contact Form 7; WPML, GravityGorms
2008 - WebDevStudios does WP; #BuddyPress, WooThemes
2009 - wpbeginner, Pippins Plugins
2010 - Yoast, Human Made
2011 - 10up, #WooCommerce