Taskful - Deadlines, meet your match.
Streaks - The to-do list that helps you form good habits.
Calendarist - Time blocking companion for Google Calendar
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Centered - Centered helps you get into a Flow State faster and stay there longer so you can do your best work.
ToDoList - Windows desktop application to stay on top of your daily tasks.