Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Clockwise - Time & attendance tracking with QuickBooks integration
Kin Calendar - The simple and connected calendar
Schedulr - Schedulr makes it easy to meet with others w/out the headache of back-and-forth emailing.
Calendly for Chrome - Schedule meetings without leaving your inbox
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.