Google Calendar - Spend less time managing your day & more time enjoying it
Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
24me - Next Generation Personal Assistant
iCal - In Calendar on your Mac, subscribe to calendars published or shared by others.
Calvetica - The fast calendar for iPhone. Add an event in just two quick taps.