Road warriors have a handy new way to find and book rental cars on the go: Yesterday, online car rental booking website CarRentals.com released an iPhone app that lets users search for rental cars and book them on their phones. The free app gives customers access to rental cars from large companies such as Hertz and Enterprise, along with smaller regional players. You can search for cars at 15,000 locations worldwide by entering an airport code, zip code, city, or by using your phone's current location. Once you find a car, you can enter your contact info and make a reservation, which you can also cancel on your phone. The app also includes information on rental policies and rental locations.