Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Qloapps - Open Source System - Build Hotel Booking Website and Manage Online & On-Desk Bookings.
TickTick - TickTickis a cross-platform to-do list app & task manager helps you to get all things done and make life well organized.
FewohBee - Web based management tool for hotels, pensions, accommodations and vacation homes
Zenkit - Zenkit is the home you always wanted for your ideas, your projects, your business.
BSI Hotel Booking System - BSI Hotel Booking System is a real time online hotel booking.