DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Communifire - Enterprise Social Collaboration Software
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Workplace by Facebook - Connect everyone in your company and turn ideas into action.
TiddlyWiki - a non-linear personal web notebook
DigitalChalk - Online Training Software and Learning Management System (LMS)