Dudle - Dudle is an online scheduling application, which is free and open source.
Pulse 24/7 - Booking & scheduling mobile app for service providers
MakePlans - Online appointment booking - MakePlans
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.
Set a Time - Appointment scheduling software for businesses to accept appointments online from customers and clients.
Scheduled247 - Schedule online appointments with your clients in an intuitive way.