Joomla Project and Open Source Matters, Inc (OSM) have just released the beta 1 of the popular open source CMS Joomla.
Here are few of the concepts from behind the new release:

Key Features in Joomla 1.6:
New Access Control System - Allows site administrators control over who can view and manage content.
Unlimited Depth Organizational Model - Gives site administrators and content creators user-defined category levels that allow for the creation of a category tree with as many or as few levels for organizing articles and other content as needed.
One-Click Extension Updates - Allows users to keep sites secure and controlled by simplifying the process of updating extensions.
Semantic XHTML Layouts - Provides a better baseline for content presentation.

The full press release article can be read here.

Do not forget that this is a beta build, and is for testing and development purposes; do not use it as main back-end for a online website until stable version is released.

We are testing the new beta, and we'll come with our opinions soon.