Content Management Systems
Content Management Systems are a broad category of applications that assist with managing webite content. The software that manages this site, MediaWiki was supposed to be a Wiki but has developed into a sort of CMS. Drupal was supposed to be a blog engine, and developed into a CMS. Even psyced, with its textdb and builtin HTTP-Server, has some CMS-like attitudes. There are countless different systems in use on the world wide web. More detailed information is available from the Wikipedia article
Conversational Monitor System
The Conversational Monitor System was an operating system for IBM mainframes which inspired lynX to implement a distributed chat system over the BITNET. It operated in a P2P fashion. That was in 1988.