RexPad - Nimble collaborative note-taking.

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

Indigrid - Plain text outliner with side-by-side views.

Bit.ai - Bit is a smart real-time document collaboration platform for teams to create interactive documents, manage digital content and track document insights.

Etherpad - Etherpad is a highly customizable Open Source online editor providing collaborative editing in...

Airborn - Create and edit documents online without sacrificing your privacy