Stuck in the airport after missing a connecting flight? There’s an app for that, as the people at Apple like to say. In truth, there’s an iPhone application for just about everything these days, especially travel. We’ve rounded up some of the best trip-friendly apps, from electronic postcards to where to find cheap gas. And don’t forget to turn off data roaming before you hit the road so you’re not whacked with some nasty surcharges when you get back. Unfortunately, there’s no app for that.

— Nicole Cammorata, Globe Staff