Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Gone - An ephemeral to-do list

EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

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

Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.