Documize - Enterprise-grade wiki and knowledge management platform
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
HackMD - Fast and flexible, real-time collaborative markdown, inspired by Hackpad.
Docsie - Docsie makes it easy to create and maintain your website documentation, without having to deploy it...
ReadMe - A collaborative developer hub for your API or code.
Dokit - The solution for disseminating know-how: work instructions, procedures, knowledge base, documentation techniques, product support, wiki enterprise.