Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
Kin Calendar - The simple and connected calendar
Microsoft Hotmail - Collaborative Calendars
Google Calendar - Spend less time managing your day & more time enjoying it
VCalendar - VCalendar is an open source Web calendar application for posting and maintaining events and schedules online.
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere