Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Dudle - Dudle is an online scheduling application, which is free and open source.
Cvent - Cvent's event management software provides event planners with a complete solution to increase event attendance and decrease event costs.
MakePlans - Online appointment booking - MakePlans
Ticket Tailor - Ticket Tailor is an easy-to-use event ticketing platform that allows event organizers of all shapes and sizes to sell tickets online.