stickK - stickK enables users to form commitment contracts to help them achieve their personal goals.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Becomr - Reach your goals, build healthy habits, & improve your life
Microsoft To-Do - Task management tool
Beeminder - Beeminder
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.