8. Foursquare
The destination-focused social network continues its rise with an app that does more than let you keep tabs on where your friends are and win badges for completing various travel-related stunts. Foursquare is also a handy to-do list maker, letting you plan what bars and restaurants you want to visit in each city your travels take you to. Android, iPhone, and other versions are available.
Free
Works on iPhone/Blackberry/Android/Palm
9. Kayak Mobile
Free
Works on iPhone/Blackberry/Android/J2ME
10. Inrix Traffic
Free (upgrade available for subscription fee)
Works on iPhone/Android
11. FlightTrack
$4.99
Works on iPhone/Blackberry/Android/Palm
12. GasBook
Cheap gas apps are a dime a dozen. For a buck, you can get arguably the best. GasBook plots fuel stations on a map, offers a clear and clean interface, and lets you bookmark your favorite stations for quick and easy access at a glance.
$0.99
Works on iPhone
13. Trip Splitter
Cheapskates of the world, unite! If you're traveling with a bunch of reckless spendthrifts, Trip Splitter gives you a quick and easy way to divide shared expenses among the travelers fairly. You can assign entries to the group or to a subset of individuals, making it easy to track who owes what to whom once you get home. The app handles foreign currencies, too.
$1.99
Works on iPhone
14. Transport Maps
No complicated explanation for this one: Transport Maps maintains a database of maps for just about every public transit system in the world. Elsewhere you can obtain interactive maps for particular transit systems--such as San Francisco's iBART and New York's KICKMap--but for one-stop shopping, Transport Maps is tough to beat.
Free
Works on Android
15. TripIt
Trip planner TripIt stores all of your frequent-flier information in one place and organizes multiple confirmation e-mail messages and itineraries in a simple, easy-to-browse list. Need to make changes? Phone numbers are automatically linked to each destination, every step of the way. Android, BlackBerry, and iPhone versions of this app are available.
Free
Works on iPhone/Blackberry/Android