Perfect World Clock - Provides easy access to the time in hundreds of cities adding several clocks as home screen widgets.
FlightAware - Track your flight by entering your airline and flight number and receive updates on flight delays, gate changes, and/or cancellations.
FourSquare - Turn on this app upon arrival and see a list of tips from those who have been there before you.
Tripit - Combine all your travel reservations in a single locations.
Hailo - Uses cell phone’s GPS to make cabs come to the user.   Available in six US cities/15 worldwide.
Trip Journal - This virtual travel scrapbook will also create maps of your various explorations as long as your GPS in turned on, geo tagged with pictures, videos, and notes.
HopStop - Offers public transport information on 68 of the world’s biggest, busiest metropolitan hubs.
Schemer - Google’s test crowd sourced travel guide.  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.
Air Sharing - Turns your iPhone into a wireless hard drive, allowing the user to quickly load documents at the airport that can be viewed in flight.
PhotoSynth - Enables users to take awe inspiring panoramic pictures in an instant and is fully integrated with Facebook.
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.
Zagat - A guide to discovering the best restaurants, bars, cafes and clubs.  Started with nine cities (Austin, Boston, Chicago, London, Los Angeles, New York, Philadelphia, San Francisco, Washington DC) with more on the way.
TravelSafe - A database of emergency service and embassy phone numbers for almost every country.
XE Currency - Quotes live currency rates.
Touchnote - Send real postcards using cell photos.