I use Joomla technology.
Joomla powers over 30% of the world's websites including large retail sites (like ikea.com). Only Wordpress has a larger footprint, but Joomla is more powerful, especially in complex user management.
Wordpress was designed intially for blogging and is a bit simpler (which gave it its numbers advantage). Joomla! is designed as a fully-featured Content Management System (CMS). It is more complex, but it excels in its ability to control user interation (with appropriate user and access control). Joomla! is highly extensible, blogs and full Social Media interactivity is easily added).
Learning Joomla! directly translates into understanding how most of the websites you use are built. Learning Joomla is a transferable skill.
Joomla! Essence
Joomla is built on Articles (similar to web pages). This is essentially The Content.
Categories are a fundamental property of Articles. It allows easy grouping of articles, which facilitate a variety of ways of presenting the Articles.
Menu Items provide an easy way to present Content.
Here are some of the ways Joomla! Menu Items can present articles:
- Single Article: the menu item points to a single article.
- Category List: this lists all the articles in a Category. Example: ORD Articles
- Category Blog: this presents a Category's articles in preview mode. Example: Expertise
- Featured Articles: this presents Articles that have their Feature field set to Yes: Featured
All the Menus can easily be changed, they have properties that are also easily changed (sort order, etc.). This can change how the content is displayed.
Articles can have unlimited Tags (keywords), which can be used in Search functions and in Menu Presentations (Show Articles that match a Tag etc.).
Finally: User Groups and Permissions. Visibilities and Capabilities can be tailored to any level of granularity. You can let people see only what you want them to see and do only what you want them to do. This enables a high level of safe and appropriate participation and contribution.
Joomla! Extensions
Basically, there is no limit to what you can do with Joomla.
It's open-source; a large community publishes add-ons; most are very powerful and free or cheap.
In addition to the Content Management, it is designed around a social interaction. You can build interactive chats, photo-galleries, and even a full Facebook-level social media experience.