Managing millions of tasks, Todoist is an online task management app and todo list. It has Web, iPhone, Android, Chrome, Firefox, Outlook flavors (and more!).

Google Tasks is a very simple task list. Works inside Gmail, Android, and Calendar seamlessly.

Any.do is a simple & powerful way to manage Projects, To-do lists & Reminders. Available on Web, iPhone, Android, Mac, Windows & More.

Microsoft To-Do is an intelligent task management app that makes it easy to plan and manage your day. With its intelligent Suggestions, To-Do removes all the clutter and empowers you to focus on what's important, when it's important.

Things is an award-winning personal task manager for Mac and iOS that helps you achieve your goals.

OmniFocus is an incredible task management platform for Mac®, iPad®, and iPhone®.

Zenkit is a flexible workspace you can use to organize the things you care about, in the way that suits you best.

TickTick is a simple and effective to-do list and task manager app with seamless cloud synchronization across all your devices.

Toodledo is one of the most popular online productivity tools available today. Use it to organize your life into list and notes.

Remember The Milk is the smart to-do app for busy people.