Check out phpWebSite:
http://phpwebsite.appstate.edu/
This is a nice Open Source Content Management system that several universities and medium businesses are using for Intranet deployments. The class structure used to develop it allows for easy customization and the template scheme is easy to use and modify.
In fact, if you are looking for a system that support CSS and "tableless" design, check out my GNU GPL theme for phpWebSite:
http://www.itwebsolution.com
Not too many dynamic sites can boast a tableless design that works well no matter how much content is loaded on the site. phpWebSite handles this with flying colors an more!
