Patrick Tisseghem has written 3 new awesome articles for MSDN on Web Content Management in MOSS.  These are a great intoduction to WCM and customizing WCM in MOSS. 

A great starting point and a must for anyone getting into this:

Customizing and Branding Web Content Management-Enabled SharePoint Sites
(Part 1 of 3): Understanding Web Content Management and the Default Features

Customizing and Branding Web Content Management-Enabled SharePoint Sites
(Part 2 of 3): Extending WCM

Customizing and Branding Web Content Management-Enabled SharePoint Sites
(Part 3 of 3): Creating and Configuring WCM-Enabled Sites