1. HotelTonight
HotelTonight helps you get discounted hotel rates, which can save major money while on your trip. When hotels have unsold rooms, they load them onto the app with discounted rates, with the hopes that you snap them up and help them sell out for the night. 

The app also has a loyalty program, where the more you use it, the more points you get that can be exchanged for room upgrades, higher discounts, or late check-outs.