DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Confluence - Confluence is content collaboration software that changes how modern teams work
Nuclino - Nuclino is a unified real-time workspace for teams that brings all your notes, tasks, and docs together in one place.
Quip - Quip is the modern productivity suite that simplifies your life and helps your team get work done faster.