RexPad - Nimble collaborative note-taking.
Documize - Enterprise-grade wiki and knowledge management platform
Indigrid - Plain text outliner with side-by-side views.
HackMD - Fast and flexible, real-time collaborative markdown, inspired by Hackpad.
Etherpad - Etherpad is a highly customizable Open Source online editor providing collaborative editing in...
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.