Plone is a user friendly implementation of the Content Management Framework
written on top of ZOPE.  Plone is a GUI/Interface/Implementation of the
CMF.  It benefits from all features of ZOPE/CMF such as: RDBMS integration,
Python/Perl extensions, Object Oriented Database, Web configurable workflow,
pluggable membership and authentication, Undos, Form validation, amongst
many many other features.  Available protocols: FTP, XMLRPC, HTTP, WEBDAV
and you can hack it to enable SOAP.  Turn it into a distributed application
system by installing ZEO.

Plone attempts to compete with Livelink, Interwoven and Documentum.  It
aims to be *the* opensource out-of-the-box publishing system.