Documize - Enterprise-grade wiki and knowledge management platform
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Boardist - Personal workspace for all the data
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
TiddlyWiki - a non-linear personal web notebook