Source: http://lifehacker.com/5750431/the-best-travel-apps-for-iphone
Your iPhone is always with you, so it makes for a great travel companion when you need all kinds of information about the places your visit on your vacations. Here are our favorite travel apps to help make your vacations a breeze.
For the flip side of the smartphone travel app selection, check out the best travel apps for Android.
Kayak
While we really like Hipmunk for flight search, they have yet to release an iOS app. Kayak, on the other hand, is good alternative and has a really nice (and free) mobile app. While I've always found the Kayak web site a little cumbersome, I find the iOS app much easier to use. Everything is cleaner and simplified. It doesn't do much more than search for flights and provide your with your options, but what else do you really want?
Kayak | iTunes App Store
TripIt
TripIt is a really great webapp, and the iOS app is an excellent extension. TripIt can connect to your Gmail (or Google Apps) account to import trip data, or you can just forward itineraries you get from booking sites or airlines to TripIt and it'll parse the information into a more useful, readable format. The mobile app makes it easy to keep all your itineraries with you and keep on top of your flights and hotel bookings. While TripIt Pro (a subscription service, not a paid version of the app) offers additional features, we think you'll find regular TripIt useful enough and won't really need to upgrade.
TripIt (Free) | iTunes App Store
PackTM
You might wonder why you'd need an app to help you pack your bags, but just wait until a bad TSA worker steals something from your or your bag gets lost. Having an inventory will suddenly seem worth the trouble. PackTM is a very simple bag-packing app that'll let you put together your bag inventories for multiple trips. To avoid re-entering items, you have a master catalogue to keep track of the items you pack. While PackTM will cost you $2, if you only need to keep track of one trip at a time the free version (Pack Free) will work just fine.
Pack TM ($2) / Free | iTunes App Store
Travel #s
Travel #s is a free directory of business numbers that'll assist you in renting a car, booking or changing a flight, and getting a room at a hotel. While it's probably easier to just book your flight online most of the time, when you're actually on vacation you might need these numbers to change reservations or get information when you don't have the comfort of all your technology. There really isn't much else that Travel #s does, but it's free and a handy bit of information to keep with you when you're on vacation.
Travel #s (Free) | iTunes App Store
Help Call
While there have been multiple occasions where I've nearly been killed on vacation, I've never had the need to call an emergency number. Still, I may be the only person I know who hasn't. While we want our vacations to go well so they're fun and problem-free, you can't always avoid an accident or unexpected emergency. Help Call is a $1 app that will connect your iPhone with emergency numbers no matter where you are. You can even set a number to dial when you shake the phone in the event you can't press the button yourself. Help Call's interface is very simple and features just a set of four buttons: police, fire, ambulance, and friend. Hopefully you'll never need it, but it's good to have for peace of mind.
Help Call ($1) | iTunes App Store
FlightBoard
For some reason, flight-tracking apps are a little bit pricy on iOS. While not the cheapest, FlightBoard is certainly not the most expensive. $4 gets you what is one of the best flight tracking apps. It's frequently updated, has a nice and simple interface (it's based on the Charles de Gaulle Airport in Paris), and lets you get a lot of flight information at a glance. FlightBoard is a combo app, meaning you get a native version for both your iPhone and iPad. While there are certainly other ways to get flight information, FlightBoard is about as quick and easy as it gets.
FlightBoard ($4) | iTunes App Store
Last, as noted in the Android counterpart, Skype is a must to have on hand if you're traveling internationally and want to make cheap calls back home. Any great travel apps you think should've made the cut? Share 'em in the comments!
You can contact Adam Dachis, the author of this post, at adachis@lifehacker.com. You can also follow him on Twitter and Facebook.