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.
Foodspotting - Focuses on specific dishes with user generated recommendations.
Perfect World Clock - Provides easy access to the time in hundreds of cities adding several clocks as home screen widgets.
Seatguru - Shows the best seats on every plane and where power ports are located.
Tipulator - Makes tipping easy even with split bills.
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.
FourSquare - Turn on this app upon arrival and see a list of tips from those who have been there before you.
Urbanspoon - Shake your phone and the Urbanspoon slot machine will suggest local popular east via the GPS in your phone throughout the US, Canada, UK, and Australia.
Tripit - Combine all your travel reservations in a single locations.
EveryTrail - Track, share and explore.  Plot your trip, photos, and video right on the map and upload it to EveryTrail, Facebook, and Twitter.
XE Currency - Quotes live currency rates.
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.
Yelp - Find places to eat, shop, drink, relax, and play and read reviews from knowledgable locals.
AlpineQuest GPS Hiking - Comprehensive orienteering maps come complete with contour lines.