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

KosmoTime - The to do list with super powers

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.

Cron - Cron Calendar.

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

Vimcal - Vimcal is the world’s fastest calendar, beautifully designed for people who work remotely and live in their calendars.