Documize - Enterprise-grade wiki and knowledge management platform
SDL Trados Studio - SDL Trados Studio is the complete translation environment for language professionals who want to edit, review and manage translation projects.
HackMD - Fast and flexible, real-time collaborative markdown, inspired by Hackpad.
HostMyDocs - Self hosting any HTML documentation
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.