Dozuki - Dozuki is a web-based tool for creating and distributing step-by-step documentation.
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
REWO - REWO is a knowledge documentation and distribution solution, which drastically improves capturing, visualizing and communicating knowledge.
TiddlyWiki - a non-linear personal web notebook
Bloomfire - Let Bloomfire help you get organized! Organize your content, build your company knowledge base and help your employees to be more successful.
Confluence - Confluence is content collaboration software that changes how modern teams work