If you’re travelling abroad with the iPhone and understandably wish to avoid AT&T’s ridiculously high data roaming charges when trying to find the train station in a new city, I would highly recommend OffMaps.
OffMaps lets you take your maps offline. It is the ideal companion for any iPhone and iPod Touch user, who wants to access maps when travelling abroad (and avoid data roaming charges) and who wants to have fast access to maps at all times. This app (and the icon) just has to be on the right hand side of Apple’s built-in maps app.
OffMaps uses OpenStreetMap that include a lot more information than simple road maps: from ATMs and train stations to restaurants and pubs! You choose which areas to download instead of buying a new app for every city you want to visit.
I used it for a week in Paris and it worked great; the GPS and compass both still work when data is off so locating yourself isn’t a problem. Just download the proper maps before you leave for your trip and you’re good to go.