There are many open source content management systems (CMS) available, and the best one for you will depend on your specific needs and requirements. Some popular and flexible CMS software options include:
WordPress: WordPress is the most widely used CMS in the world and is a popular choice for bloggers and small businesses. It is easy to use and has a large community of developers who contribute themes and plugins to extend its functionality.
Joomla: Joomla is another popular CMS that is suitable for both small and large websites. It has a wide range of features and is flexible enough to be used for a variety of different types of websites.
Drupal: Drupal is a powerful and flexible CMS that is popular for large and complex websites. It is designed for developers and offers a wide range of features and modules to extend its functionality.
Magento: Magento is an open source e-commerce platform that is popular for online stores. It offers a wide range of features and is flexible enough to be customized for a variety of different types of stores.
Ghost: Ghost is a lightweight and open source CMS that is designed specifically for bloggers. It is easy to use and offers a simple and clean interface.
Ultimately, the best CMS for you will depend on your specific needs and requirements. You may want to consider factors such as the level of complexity, the type of website you are building, and the level of customization you need.