Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Kin Calendar - The simple and connected calendar
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere
Google Calendar - Spend less time managing your day & more time enjoying it
Zynq - Schedule meetings from an email with 1 click!
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.