The number one free and open source (foss) blogging software WordPress has contributed much to the web from its launching to this very minute. Might it be WordPress stand-alone or the Automattic maintained WordPress.Com blog hosting. Either way, you can be assured that what you get is quality, and that for free.
Matt Mullenweg, the lead developer of WordPress has been recognized for this unflagging success once again, being one of the top 25 most influential people on the world wide web. Some people say that he just ranked fourteenth is quite weak, others say it appeals very strong. Well, all that I can say (in which a lot of people would agree with me) is that the rankings is not based on any criteria (within the top 25) but they have been alphabetically arranged. What counts here is that Matt is one of them, and heck, job well done so far!