Joomla! is an extremely popular open source content management system (CMS). I've been getting a lot of calls from clients wanting Joomla!-based sites, because this very powerful system allows non-technical people to manage the content (words and pictures) on their own site. And it's free! Much like iPhone apps, there are countless components that expand the core functions of a Joomla! site and allow it to do amazing things for only a few dollars.