TicketPeak - Online Ticketing Software
MakePlans - Online appointment booking - MakePlans
Audience View - Audience View is a cloud-based ticketing solution created for the performance arts industry and suitable for both profit and commercial uses.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
TicketingHub - Next generation of Ticketing
Dudle - Dudle is an online scheduling application, which is free and open source.