WordPress is a free content management system. It was programmed from 2003 by Matthew Mullenweg as software for weblogs and is constantly being developed as an open source project. WordPress is the most widely used system for running websites with about 50% share of all CMS or 32% share of all websites.
For small customer projects with manageable requirements, I like to rely on the easy-to-use and low-maintenance content management system. The blog system can be adapted to their requirements at low cost thanks to the large selection of available themes and plugins.