Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
Clearbit - Clearbit provides Business Intelligence APIs
Campaign Calendar - Campaign Calendar by Bracket Labs builds a marketing calendar from your Salesforce Campaigns.
Memotoo - Memotoo allows you to sync your data (contacts, calendar, tasks, .) with phones (iPhone, Android, Samsung, ..
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.
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.