1. Twitterific (free): While Walt likes Tweetie we have to go with Twitterific which is free and allows us to take pictures with our iPhone, pictures that get instantly converted into a TwitPic link and embedded in our tweet. And if you're traveling, you want everyone to know all the cool things you've seen right? Also, Twitterific is good for facilitating Tweet-ups and getting your questions about a new city, an airplane delay or transpo options answered faster than you ever thought possible.
Our only complaint however is that usually when you open Twitterific on your phone, you have to scroll up to see the latest tweets. But when @lancearmstrong finally @replies to us, we'll be able to see it clearly as those are highlighted in brown. (Direct messages are highlighted in blue.) It's way better than relying on Safari to sign-in to Twitter.
2. Flashlight (free): One of our friends swears by this application which acts as a nite-lite whenever you need it--whether it be out camping in the jungle, reading a novel in your hostel so as not to disturb your strange new roommates, during a power outage at your five-star hotel or on the plane when your overhead light is malfunctioning.
The app fills your iPhone screen with a bright white screen but you can change the color depending on your mood. Hence, mood lighting. You can also dim and brighten the screen to your preference as well as put it in "trippy" strobe lighting modes. And don't forget to hold it up at the Led Zeppelin Tribute Band concert.
3. Facebook (free): While we're more likely to update our trip details on Twitter than Facebook, you can't underestimate the addictive power of Facebook on your iPhone. It's the best way to kill time when you're waiting at the gate or if you've been off the grid for a while and miss your friends and family.
This application works way better than the Facebook for Blackberry application. You can scroll through your friends' drunken karaoke pictures, review everyone's status updates, stalk ex-boyfriends and girlfriends and instantly approve that Friend request from your 7th grade biology partner who split town soon after you split the frog together.
However, if you get a little too eager browsing a friend's photos, the app can freeze your phone, forcing you to restart it.
4. Units (free): Of course, your iPhone apps can't be all fun and games. A few of them should serve more useful purposes, especially when traveling. We like Units which can convert all types of measurement and most importantly, currency. It evens has a small ruler which you can break out when...um...well, we're not quite sure we've ever needed a ruler while traveling. But still, it would be cool to whip it out just because.
5. Scrabble ($4.99): So this is the only application that we've ever paid for and we don't regret it at all. Scrabble saved us on an overnight flight to Paris when the two schmoes in front of us decided to stay up all night playing cards and charming the flight attendant for more and more drinks.
With three hours left in the flight, we turned to our traveling buddy and engaged him in a game of Scrabble, four times over. This version of Scrabble allows you to play either the game or another person. Plus, it's a little easier than regular Scrabble as a "Best Word" function helps you maximize whatever tiles are sitting on your shelf.
It's much more convenient than a portable Scrabble boardgame and a heck of lot easier to clean-up. Just make sure you are constantly charging your iPhone to keep the juice going during your games.
Shazam: This app is crazy cool. If you're fiddling with the radio in your rental car and a song comes on that you really like but have no idea who sings it, you can hold up your iPhone (with Shazam open) and the app will find out the artist and the song name. It will even point your towards the iTunes store to purchase the song or YouTube to watch the music video.
Translator: It will work in a pinch if you need to translate any signs or directions. It can also help you with certain phrases that you might need to get by in a new country. ("Where is the bathroom?" type of phrases.)
Restaurant Nutrition: So you and your diet never have to part just because you went on vacation. This app tells you the calorie and fat content in all of your favorite chain restaurant foods. But you may not want to look. And if you do, don't ruin it for the other folk in your party. Nobody wants a Debbie Downer when they are eating their double-double from In-n-Out.
There are thousands of cool other iPhone apps out there but we wanna know, which apps do you use the most when traveling? Tell us in comments below.
[Top photo of iPhone: RobinHamman]