Mambo (formerly named Mambo Open Source or MOS) is an open source content management system (CMS). It features a page caching mechanism to improve performance on busy sites and automates many tasks for a static website like web indexing. Mambo can provide RSS feeds, PDF versions of pages, news flashes, blogs, internet forums, polls, calendars, website searching, language internationalization, and other possibilities. Mambo Open Source requires Apache, PHP and MySQL to work properly.

Mambo is a full-featured content management system that can be used for everything from simple websites to complex corporate applications. Continue reading for a detailed feature list:

Source code is completely free.
A large and healthy user and developer community.
Provides a basic level of content approval for registered users.
Online help.
Page caching mechanism to improve performance on busy sites.
Trash manager
Advertising management (banners, etc).
Media (images, documents) upload and management.
Content display scheduling.
Content syndication (RSS).
Search engine friendly (SEF) URL's.
Internationalization (interface translation).
Content macro language (aka mambots).
Advanced and separate system administration system.
Advanced package/addon/template deployment system.
Simple but powerful template system (written mostly in HTML, no complex templating syntax to learn, just a couple of PHP functions to include).
Hierarchical user access groups.
Basic visitor statistics.
Multiple WYSIWYG content editor support.
Simple polls.
Content voting/rating system.null

Many more free add-ons are available at mamboforge.net. Some of these add-ons include:

LDAP authentication
Extended user profiles
Forums
Media galleries
Document managers
Templates
Events calendar
and many, many more...