For an overview of CMS for a non-technical audience, try James Robertson’s excellent site:
http://www.steptwo.com.au/
Also try:
http://www.designit.com.au/articles/rebuilding_gradlink
More CMS Tutorials
The new CMS Wiki has a definition of a Content Management System.
http://www.cmswiki.com/tiki-index.php?page=ContentManagementSystem.
It also has a discussion of the confusing term portal.
http://www.cmswiki.com/tiki-editpage.php?page=Portal
And something on Workflow.
http://www.cmswiki.com/tiki-index.php?page=WorkFlow
CMS Review has references to all the great books on Content Managemant.
http://www.cmsreview.com/Resources/Books.html.