FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Qloapps - Open Source System - Build Hotel Booking Website and Manage Online & On-Desk Bookings.
Dudle - Dudle is an online scheduling application, which is free and open source.
FewohBee - Web based management tool for hotels, pensions, accommodations and vacation homes
Mobile-Calendar - Reservation management system. If you rent accommodation, the mobile-calendar app was made for you!
BSI Hotel Booking System - BSI Hotel Booking System is a real time online hotel booking.