Taskful - Deadlines, meet your match.
Cron - Cron Calendar.
Streaks - The to-do list that helps you form good habits.
KosmoTime - The to do list with super powers
ToDoBook - Turn your Facebook (& other social media) News feed into a to-do-list.
Vimcal - Vimcal is the world’s fastest calendar, beautifully designed for people who work remotely and live in their calendars.