1. Skype

All you need is a wifi hotspot to make Skype-to-Skype calls free from your iPhone. The rates for calls to mobiles and landlines (both national and international) are affordable. You can also keep track of who’s online to send and receive instant messages.

Skype offers both pay as you go credit plans or a subscription that offers unlimited calls to landlines and cell phones (in some countries).

Price: FREE

2. Cheap Gas

This app, created by OPIS (Oil Price Information Service), gives you a head start on the hunt for the best gas prices. Cheap gas uses the iPhone 3G’s GPS feature to find the ten gas stations in your area with the cheapest prices.

For the more discerning gas customer, Cheap Gas offers an advanced search function to specify zip code and type of fuel (unleaded, premium unleaded, or diesel).

Price: FREE

3. Saucy Phrasebook

This language app by SoSauce is a little different from the rest. Rather than asking where the bathroom is, the Saucy Phrasebook contains such useful phrases as “I drank too much and I’m going to puke” and “Help! I just got swindled!”

Each phrase is recorded in Mandarin, French, Hindi, Japanese, Spanish, and Russian by native speakers.

Price: FREE

4. Flight Track Pro

This app tops our list as far as price goes, but if you’re a frequent flyer, reviewers claim Flight Track Pro is well worth the price of a pizza. When you book your flight, simply forward your confirmation email to plans@tripit.com, and your itinerary will appear automatically on your iPhone.

Flight Track Pro keeps you up to date on your flight status, airport delays and closures, gate numbers, and the weather forecast for your final destination.

Price: $9.99

5. goPostal

For $1.29 in postage costs, you can send an actual personalized postcard via the U.S. Postal Service. Simply select a picture from your iPhone, add a message, and send to any address in your phone book. The postcard will arrive within 24 hours.

These postcards make for a great, affordable souvenir without taking up luggage space.

Price: FREE (plus cost of postage)

6. Find Internet Cafe

For those that need wi-fi served along with their latte, the Find Internet Cafe app…well, does this really require an explanation? The app automatically detects your location and offers a list of closest internet cafes, complete with an interactive map, driving directions, the phone number for the business, and the cafe’s website. The bookmark feature allows you to save your favorites.

Of course, you have to be in a wi-fi zone for the app to work. And for now, Find Internet Cafe only offers suggestions inside the U.S.

Price: $0.99

7. iCarPark

Never forget where you parked again! iCarPark allows you to save your parking spot on a map. It then provides walking directions back no matter where you are.

Extra features allows you to keep track of meter times, remember parking garage levels, and keep track of up to five parked vehicles.

iCarPark also gives the option of using a satellite hybrid map for even better navigation!

Price: $0.99

8. SitOrSquat

The beauty of this app is in its name. Sure, there are a few apps that will help you locate the nearest restroom. But if you’ve traveled through certain countries, you know that a Western toilet is still only really common in the West.

Using the iPhone’s GPS features, this app will tell you which of the almost 60,000 restroom locations registered with SitOrSquat is closest to you, and whether or not you need to warm up your leg muscles before entering. SitOrSquat also provides information on changing tables, handicapped facilities, and a little bit of humorous bathroom reading.

Everyone is encouraged to enter any new public restrooms they stumble across to the system; it’s all about helping each other out.

Price: FREE

9. Stanza

It’s pretty easy to see why Stanza is one of the most popular eBook readers out there. With a built-in catalog of over 100,000 books and the ability to personalize fonts, colors, and page setup, Stanza already has more than a million customers.

If you already have a few eBooks or documents, you can transfer them over to your iPhone with Stanza by using the free desktop app for Mac & PC.

Price: FREE

10. AroundMe

If you aren’t app-happy and want get as many features as possible from just one travel app, AroundMe is the way to go. This app uses the iPhone’s GPS feature to locate anything and everything you need, including banks, bars, gas stations, hospitals, hotels, theaters, restaurants, markets, and more.

You can see your destination’s location on a map, view the most direct route, and save it in your contact list. AroundMe also has a Nearby listing that uses Wikipedia to find what else is close to your location.

Price: FREE