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.
Any.DO - The #1 task management app used by over 11 million people globally, Any.do is your free mobile and online task manager for Android, iPhone, Web and more.
Everlist Task Manager - Groceries, trips, errands, and daily todos managed simply. get your tasks under lovely control.
Microsoft To-Do - Task management tool
Taskful - Deadlines, meet your match.