Plone

Plone is a free and open source content management system built on top of the Zope application server. In principle, Plone can be used for any kind of website, including blogs, internet sites, webshops and intranets. It is also well positioned to be used as a document publishing system and groupware collaboration tool. The strengths of Plone are its flexible and adaptable workflow, very good security, extensibility, high usability and flexibility.

Plone is released under the GNU General Public License (GPL) and is designed to be extensible. Major development is conducted periodically during special meetings called Plone Sprints. Additional functionality is added to Plone with Products, which may be distributed through the Plone website or otherwise. The Plone Foundation owns and protects all copyrights and trademarks. Plone also has legal backing from the council of the Software Freedom Law Center.

MediaWiki's "Monobook" layout is based partially on the Plone style sheets.

Installation

Plone is a lot bigger (36M) than most of the PHP based CMS's probably because it contains Zope and it's own version of Python. I ran through the installation setting it up as standalone with all default options. But now I'm not quite sure how to "get to it" from the browser...? - definitely not a noob-friendly installation compared to the standard LAMP-based software.