If you have an Android-based phone and you want to instantly get more organized, check out the new client app for Android of Remember The Milk. Remember The Milk is a long-standing to-do list manager that many people on Windows and Mac systems absolutely swear by. It's not a calendar, but a task manager that makes it very easy to enter tasks, set deadlines and reminders for them, and see overviews of things you need to get done soon. As JKOnTheRun notes, there is an iPhone version of it, but the Android version can synchronize tasks in the background rather than requiring you to open the application every time you want to synchronize. The app is free for Android users, but does require a $25 yearly Pro account.