CMS / Portals
There are a million different Content Management Systems (CMS), or portals as there known, out there.  Many are free open source solutions, and many are full blown enterprise level applications that cost an arm and a leg to license.  What's right for you is a matter of your personal needs.  There is no one solutions fits all when it comes to CMS applications.

Some CMS applications are extreamly robust, while others pride themselves on being lightweight.

Do CMS's really count as web application?  That's really a matter of opinion.  Web technology has come so far that hardly anyone writes static HTML pages, but the admin site of CMS's can be extreamly powerful and would certainly qualify as a web application.