"CMS" is the common initialism for "Content Management System". I work mostly with CMSs based either on Python (Plone/Zope, Turbogears, Django, ...) or PHP (Joomla! and Drupal), although I had early experience with Tcl-based frameworks such as AOLserver and ... I've done a little with SharePoint as well.
"11 Questions to Ask CMS Job Seekers" reflects much of what I know on the titular subject.