One of the most widely used tools, WordPress is an open source blog publishing application and can be used for basic content management. Powered by PHP and a SQL data backend, Wordpress is used by 62.8 million websites in the US and 202 million websites worldwide.
WordPress has a templating system, which includes widgets that can be rearranged without editing PHP or HTML code, as well as themes that can be installed and switched between. The PHP and HTML code in themes can also be edited for more advanced customizations. WordPress also features integrated link management; a search engine-friendly, clean permalink structure; the ability to assign nested, multiple categories to articles; multiple author capability; and support for tagging of posts and articles. Automatic filters that provide for proper formatting and styling of text in articles (for example, converting regular quotes to smart quotes) are also included. WordPress also supports the Trackback and Pingback standards for displaying links to other sites that have themselves linked to a post or article.
Almost everything on WordPress.com is free, and the site states that things that are currently free will remain free in the future, but that they do offer paid a la carte upgrades for things like CSS editing and custom domains.