Apps are changing the way we travel one download at a time. I *love* travel guide books, but compared to apps, they are like phone books -- you have to flip through a bunch of pages to find the info you're looking for. In contrast, apps are immediate, not to mention the bonus updates they automatically download so the info remains fresh and you don't need to buy a new edition.
Example
Here's an example of how apps are changing the way we travel. Let's say you're going to Europe for a summer getaway. Here's what you might bring:
10 YEARS AGO
One big guidebook or several country-specific ones, a language-learning tape or CD, walkman or diskman, tapes or CDs, foreign language dictionary/phrase book, airline tix, hotel & rental car confirmations, books, newspaper, maps, itinerary, mobile phone, camera
NOW One iPhone, iPod Touch or iPad will give you: country guides, museum tours, language guides, tube or metro maps, country maps, gps, airline or car rental apps to show boarding passes or car rental confirmations, trip itinerary, postcard app, books, newspaper, web browser, camera (for iPhone), photo editing, music player, TV/movie player, email client, etc...
Other than clothes, it seems like the only thing you can't bring with you on your iPhone is your passport, although I'm sure that's coming. There's also the battery issue, but if it gets drained, you'll have to rely on your ability to talk to strangers, rely on people and travel like its 1999.
[photos by ben atkin & barnacles hostels]