As of 2011, estimates are that 25% of all websites are published with WordPress. As of March 2012, WordPress is on 72.4 million sites in the world
ManageWP.com helps users manage their websites from one dashboard, keeping them all in one place, easy to access, updated and secure.
Within three months of launch, ManageWP already manages over 100,000 websites.
See more at http://managewp.com