Ghostnote - Add notes to anything.
Quip - Quip is the modern productivity suite that simplifies your life and helps your team get work done faster.
Box Notes - Box Notes: take meeting notes, share status updates and plan projects together instantly. Online, across devices.
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.
Somnote - More often than not, note-taking is a pressing, off the cuff movement that requests a quick and productive approach.
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.