Apple iWork - iWork is an office suite by Apple.
Quip - Quip is the modern productivity suite that simplifies your life and helps your team get work done faster.
OnlyOffice Docs - OnlyOffice Docs is an effective document creation and editing platform that provides you the options to create any kind of document with the collaboration of your team from any remote location.
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.
Airborn - Create and edit documents online without sacrificing your privacy
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.