Gone - An ephemeral to-do list

HeySpace - HeySpace is the only free task and simple project management software with communication and collaboration feature.

Streaks - The to-do list that helps you form good habits.

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.