When I Work - When I Work is an employee scheduling and communication app using the web, mobile apps, text messaging, social media, and email.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
Deputy - Deputy is a software for employee scheduling, time and attendance and communication management.
MakePlans - Online appointment booking - MakePlans
ResourceGuru - The fast, simple way to schedule people, equipment, and other resources online.
Dudle - Dudle is an online scheduling application, which is free and open source.