Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Microsoft To-Do - Task management tool
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
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Taskful - Deadlines, meet your match.