Azendoo - Azendoo is a collaborative task management solution that helps companies to get work done easily and in teams.
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.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Basecamp - A simple and elegant project management system.