Drupal and
Joomla are, in my opinion, the 2 most popular open source content management systems. Joomla has almost 2000 extension programs, most of which are free. I do a lot of non-adult work using Joomla -- the reason for me not being here lately -- and all of my clients are very happy with the software. I am in the midst of developing an adult site with Joomla. I will let you know when it is ready if you want to take a look at it.
Regards,
---art