Check out
www.drupal.org....
I have been building a replacement for our website using wordpressMU, joomla and drupal...
Drupal is winning hands down. A bit of a learning curve to get into the darned thing, but I cannot see any limitations with the CMS. The modules like CCK, VIEWS basically allow you to build any conceivable block, page or whatever.
Need a gallery for example... No need to find and install one, use the modules to make your own custom fields, forms, views.
In the past 2 months I have 'messed' with xoops, wordpress, joomla, mambo, glfusion, etc, etc and drupal makes them all seem pathetic.
Joomla,
I found it to be the worst.
The usergroups are not customisable to any great effect, most of the bridges do not work, any decent module is commercial and half of the mods I have tried are not wc3 compliant or cross-platform...
If you are anything like me you will have taken a look at Drupal, read nothing, achieved nothing and moved away from it... I did this last year, this time around I read the documentation for getting started and now it makes sense to me, is NOT easy to use and seems overly complicated at first, but all soon falls into place and their approach actually makes customisation very easy.
modules for custom builds
views
ctools
cck
webform
There are other dependencies, but each only enhance what you can do.
date
calendar
flag
By combining these different modules you can create any conceivable data collection / query.
Drupal allows you to modify profile fields, run multiple sites / subdomains, forum, file share, blogs, articles, permissions out of the box.
http://drupal.org