Drupal (lastest version: 7.14)

Drupal is open source software maintained and developed by a community of hundreds of thousands of users and developers. It's distributed under the terms of the GNU General Public License (or "GPL"), which means anyone is free to download it, share it with others, and contribute back to the project. This open development model means that people are constantly working to make sure Drupal is a cutting-edge platform that supports the latest technologies that the Web has to offer.

Drupal is a publishing platform created by our vibrant community and bursting with potential. Use as-is or snap in any of thousands of free designs and plug-ins for rapid site assembly. Developers love our well-documented APIs. Designers love our flexibility. Site administrators love our limitless scalability.

Rate: 4/5

Demo:  http://www.opensourcecms.com/demo/1/183/Drupal

Download the lastest version: http://drupal.org/download

Or download old versions: http://drupal.org/node/3060/release