Generally, I think your talking about a content management system. A system were users can register, and based on permissions and features, be able to manage numerous services and data posting like news, ecommerce, and other features?
Some of the more popular ones are like Wordpress which is more of a blogging type of content management system, and there are others like Joomla, Mambo, Drupal (a little more ecommerce related), and then boils into other systems for more niche type of content.
Usually, there are forums that integrate to these systems so you have 1 login for content mangaement and forum logins. Language wise, it can differ too as there are more popular ones per language. For example, wordpress is a good php cms, and there are others for the .net or java type of web coding.
Here are some of the php content management systems...
Mamboserver.com - Home
Joomla!
drupal.org | Community plumbing
Here's a couple .net content management systems...
Umbraco - The Friendly CMS
Sitefinity ASP.NET CMS ? .NET Content Management System by Telerik
DotNetNuke - The Leading Open Source Web Content Management Framework for ASP.NET
http://n2cms.com/