Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Toodledo - Toodledo provides a set of tools to increase the productivity.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
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.
Workflowy - A better way to organize your mind.
Pocket Informant - Pocket Informant is the Best Calendar app for mac and iOS. Pocket Informant for iOS, Mac desktop, and Android.