Drupal: vs Joomla, Expression Engine CMSs
Apologies for the blogging hiatus. Chances are I'll end up just providing a Social Networking distribution based on Chingri Maach's configs, before I get around to completing the walk through.
In the mean time, here are some interesting Alexa statistical comparisons of content management systems. Drupal and Joomla are the free and open source heavies, while Expression Engine is a popular commercial product. While mostly used for blogging, it also allows for CMS-like features, so I threw Wordpress into the first mix.
n.b. Visit's to the CMS' homepage (and Google search trends) are only loosely representative of the CMS's popularity.
Alexa's Reach statistics for Drupal, Joomla, Wordpress, and EE. Reach is typically expressed as the percentage of all Internet users who visit a given site. e.g. Wordpress' reach of 1.5% means that of all global Internet users measured by Alexa, 1.5% of them visit wordpress.com.

Alexa's Reach statistics for Drupal, Joomla, and EE.
Alexa's Rank for Drupal, Joomla, and Expression Engine. Rank is based on aggregated historical traffic data from millions of Alexa Toolbar users and is a combined measure of page views and users (reach).
Alexa's Page Views for Drupal, Joomla, and Expression Engine. Page views measure the number of pages viewed by Alexa Toolbar users.

neemie:
For an updated Drupal vs Joomla vs Wordpress look: http://neemtree.com.au/backing-drupal-big-way