Plone

Plone is a content management system that is simple to set up, maintain, and modify. It is designed to be a corporate-ready content management system. Plone is ideal as an intranet and extranet server, document/Web publishing system or a groupware tool for collaboration between separately located entities. It aims to be a proper content management and publishing system, sharing the same qualities as Teamsite, Livelink, and Documentum.

Homepage: http://plone.org/