1. Airline App
Almost every airline these days has their own app which passengers can download. These apps allow you to keep track of your booking, review the flight status and download your boarding pass. Highly convenient as you don't have to continually check emails or worry about which sheet of paper is the right one.
2. TripIt Travel Organiser.
The "TripIt" app is a handy one to keep your entire itinerary in one place. Here you can store your flight information, hotel, car rental etc. Which is very useful if, like me, you have a habit of forgetting those vital bits of information such as hotel names, reference numbers and such.
The TripAdvisor app is fantastic for checking out what to do wherever you are. Whether you want to see how good a certain restaurant is, what attractions are nearby or which street has the nicest architecture or shopping malls, TripAdvisor gives it all to you at the touch of a button.
4. Hotel Tonight
You never know what can go wrong on holiday, you may have a delayed/cancelled flight or as happened me, you may miss a flight (See here). This is where the "Hotel Tonight" app comes in. It shows you hotel rooms available on last minute deals, saving you both time and money.
One of the top travel apps on the apple app store at the moment. HailO finds your current location and can call a taxi right to you. Very useful if you find yourself lost in a foreign city without a number for a taxi or a notion on how to use the public transport system (trust me it happens).