Easily the best and most intuitive all-in-one travel organizer, TripIt is available for both iPhone and Android users. Once you connect your email and TripIt account, the app pulls any booked travel emails you receive and magically creates a master itinerary for each trip. Information is automatically organized and easy to read — even if you lose WiFi. There's also an option to forward trip plans to family and friends, so your loved ones always know where you're supposed to be and when (an invaluable safety precaution every traveler should take advantage of).
TripIt is completely free to use, but the pro version ($49/year) includes extra helpful features like real-time flight alerts, gate changes, and cancellation updates. TripIt Pro will even look up alternate routes if your flight is canceled.