MakCorps - Hotel Price Comparison API
TripRebel - Book your hotel now & get a refund when the price drops
Gopher - Better hotel deals automatically, every time + cash back
One Night Standard - Same night reservations at all Standard Hotels
Hotel Room Alerts - Snag a room at a sold out hotel
Sponstayneous - It's like Scott's Cheap flights, but for Airbnb's.