Dudle - Dudle is an online scheduling application, which is free and open source.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
Pulse 24/7 - Booking & scheduling mobile app for service providers
MakePlans - Online appointment booking - MakePlans
Launch27 - Online booking & appointment scheduling.
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.