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

Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

Notesnook - Notesnook is a simple and private note taking app that keeps your notes organized and synced on your phone, tablet and computer.

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Note Board - Productivity app. Save information like a sticky notes.