Dudle - Dudle is an online scheduling application, which is free and open source.
MakePlans - Online appointment booking - MakePlans
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
Framadate - Make your polls
Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.