Schemer - Users leave recommendations for things to do in their city and visitors can add to a to do list and check off as they go.
HearPlanet - The world’s largest audio guide pulls information from Wikipedia and its own database. Similar to audio guides handed out at museums.
ExpertFlyer - Get notified when seats become available.
WhatsApp Messenger - Provides the ability to send data (including pictures, videos, sound clips, and GPS tags as well as text) via Wi-Fi for free to people anywhere in the world.
Knapsack - Plan your trip and later share memories.
Passbook - Passbook is an application in Apple’s iOS that allows users to store coupons, boarding passes, event tickets, store cards, generic cards, and other forms of mobile payment.
FlightTrack - Follow international flights with detailed information on departure gates, delays, and cancellations.
Hailo - Uses cell phone’s GPS to make cabs come to the user.   Available in six US cities/15 worldwide.
Pin Drop - Allows users to drop GPS pins onto a map while traveling of interesting spots or review user made lists recommending the best sights, sounds, and flavors in town.
Tripit - Combine all your travel reservations in a single locations.
TravelSafe - A database of emergency service and embassy phone numbers for almost every country.
RoadNinja - Always know what is coming up at the next exit and compare gas prices at upcoming exits.
Where To? - Enables user to locate almost anything nearby, including the nearest ATM, burger joint, and medical provider. 
The Weather Channel - View current weather, hourly, 36 hour and 10 days forecasts.  Will forecast weather throughout the United States.
Evernote - Take notes, capture photos, create to do lists, record voice reminders, and make these notes completely searchable. Users can combine and share travel notes.