There is another CMS System that is drawing people from postnuke.
Is Mambo Open Source, its availble for free from
www.mamboserver.com and a huge community for it is availble at
www.mamboportal.com
It is a new release which has some great features.
It offers everything you could want, easy to make changes and is availble on linux, aapache and microsoft.
The community at mambo server forums and mamboportal offers lots of help, there are loads of tempalte, modules and components downloads.
Its better than postnuke.
I used it for my clients, in the OIl and Gas industry and it has atracted alot of interest and provided a profesional company profile.