StayNTouch - StayNTouch provides a full-featured mobile PMS and guest engagement capabilities.
MakePlans - Online appointment booking - MakePlans
rezStream - rezStream is a hotel reservation software for your small to the mid-sized hotel that helps you grow your business and save time.
Appointment Booking Calendar - With the Appointment Booking Calendar you can accept online bookings from a set of available time-slots in the calendar.
SkyTouch Hotel OS - Hospitality property management
Dudle - Dudle is an online scheduling application, which is free and open source.