EventTitans - Top rated event management software

Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.

Tix - Tix is a state-of-the-art, cloud-based ticketing system that features fully integrated access controls, event management controls, multi-channel distribution capabilities, and a robust reporting suite.

MakePlans - Online appointment booking - MakePlans

Brushfire - Brushfire offers tools for online registration and event management.

Dudle - Dudle is an online scheduling application, which is free and open source.