Google Calendar - Spend less time managing your day & more time enjoying it
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
Jorte - Schedule books must be practical and has a good design.
Campaign Calendar - Campaign Calendar by Bracket Labs builds a marketing calendar from your Salesforce Campaigns.
Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.
ApPHP Calendar - ApPHP Calendar is a PHP calendar script that may be easily integrated and used with various PHP projects, such as schedulers, event, etc.