K.BOOTH Joomla is an excellent content management system. I've been using it and its predecessor (Mambo) for years. The package runs well on my own and remotely hosted sites. I use with *nix, PHP, and MySQL. It is flexible, extensible, and relatively easy to setup and maintain. End-users can add and edit content, which is a real bonus for community, non-profit, and company sites that want to outgrow the single webmaster/chief editor model.
Joomla is not, however, a Mac application and may be confusing to some by having it posted here.
(Version 1.0.9)