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

doo - A smart, simple app for reminders and to-dos

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.

Laverna - Laverna is a JavaScript note taking application with Markdown editor and encryption support.

Remember The Milk - Remember The Milk is a task and time management application for mobile devices.

OneNote - Get the OneNote app for free on your tablet, phone, and computer, so you can capture your ideas and to-do lists in one place wherever you are. Or try OneNote with Office for free.