Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Google Calendar - Spend less time managing your day & more time enjoying it
Kin Calendar - The simple and connected calendar
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
Calendly for Chrome - Schedule meetings without leaving your inbox
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.