Mobile-friendly, minimal, private, and open-source. Works great on your phone as an add-to-homescreen web app, and there is no lock-in with pre-paid hosting.
Topics - Description Get organized with TOPICS to-do task list manager. Features include
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Things - Things is an easy to use task manager.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
FCorp My Calendar - Manage diary/note, schedule, todo, birthday, etc.
Google Tasks - to-do list app that integrates with Gmail and Google Calendar