Powered by Google Translate, iTranslate is incredibly easy to use. Simply set your base language, the language you want to communicate in (out of 52 different languages) and then type in what you want to say. The app will translate the text at the press of a button.
If you want the app to speak out the translated phrase, there are add-on voice packs that cost $2.49 a pop. There's also a $1.19 premium version which allows you to use the app in landscape mode, save your favourite translations and view your translation history.
Admittedly, you can access many of these functions through Google's iPhone app, which will pop open Safari to operate. But there's something a bit more practical about a dedicated translation app, and this is our favourite.