Wordpress (Wordpress.org, not to be mixed up with Wordpress.com)is the most popular open source CMS on the internet today.Wordpress was established way back in 2003 as a blogging platform and has since evolved into a fully functional CMS widely used on any type of website. You can find huge Fortune 500 companies using Wordpress, the official Facebook blog or just any news site.
Wordpress' market share is currently around 27% of the entire internet, and almost 60% of common CMS platforms.
Being such a popular CMS, there are many vendors out there, selling great designed and structured Wordpress themes and plugins.
Check out some of the popular ones below.