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.
UpNote - A beautiful and clean cross-platform app for notes organizer
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Notesnook - Notesnook is a simple and private note taking app that keeps your notes organized and synced on your phone, tablet and computer.
Slack - A messaging app for teams who see through the Earth!
Note Board - Productivity app. Save information like a sticky notes.