The remaining blogs in the top 100 list use a variety of other platforms such as Blogger, TypePad, Tumblr, in-house tools, and more. WordPress truly has grown into the number one choice for power blogs and bloggers.
Of course, blogs that run on WordPress could be hosted by WordPress (wordpress.com) or via a third party host (wordpress.org). Of the top 100 blogs, WordPress.org is 4 times more popular (39 sites) than WordPress.com (9 sites).
You can see all the details and easy to read charts on Pingdom.com.