The TripAdvisor Symfony PHP SDK by Steven Pennington integrates travel recommendations via unofficial API interaction. Installation available. Configuration presents key, cache, service, and lifetime of vacations' recommendations.
Travel booking giant Expedia, through its Expedia Affiliate Network, has launched EAN Rapid, a new platform for travel accomodation search and booking. The platform contains a number of APIs, including Geography, Shopping and Booking APIs, that affiliates can use to build booking applications.