Pulse 24/7 - Booking & scheduling mobile app for service providers
Calendly - Say goodbye to phone and email tag for finding the perfect meeting time with Calendly. It's 100% free, super easy to use and you'll love our customer service.
MakePlans - Online appointment booking - MakePlans
HeySummit - Pain free online summits, that deliver.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.