Plone is an open source web content management system developed to make intranet-, internet- and extranet publishing an easy process. It has strong collaborative qualities, and is ideal for working groups or community building efforts, as well as integrating portal services.

Plone is Free!
Really, truly free — not some crippled marketing twist or limited use policy.
Download Plone from plone.org and try a full, working CMS solution with no restrictions that will scale to fit your organisation.

Plone offers integration with a multitude of different systems, and is platform-agnostic – running on Windows, Mac OS X, Linux, BSD and Solaris. It's constructed to be as extensible as possible, and plugins/adapters for all major database systems and file formats exist.

In addition, Plone builds on its own set of innovative components that make content production and content management a fast and predictable mode of work. It uses workflow policies to govern security and access, which ensures that everyone are able to publish content without knowing anything about the underlying security implementation – and still have a safe, effective system for publishing their material online or internally.

• Technical overview of Plone