You may know Kayak as a Web site where you can find flights from a lot of different travel sites, but the app for the site is actually a much more useful travel tool. While it, of course, lets you search sites for good deals, the app also comes with neat features such as a currency converter, packing list and information about airline fees, all of which make it a great travel companion. It even has an airline directory that lets you look up customer-service lines and maps of airports around the world. Of course, those looking for fares and hotel rooms can still search using Kayak’s results, including a price tracker that may indicate the best time to buy. Once you book, users with Kayak accounts can also send their confirmations to the service for a comprehensive itinerary. Free, for iOS, Android and Windows devices.