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

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.

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

SSuite Sticky To Do - SSuite's Sticky To Do app gives you an easy way to track your tasks and organize your day.