Google Calendar - Spend less time managing your day & more time enjoying it
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Jorte - Schedule books must be practical and has a good design.
Things - Things is an easy to use task manager.