Skype

We're loving Skype: calls from Japan to UK landlines for 1p per minute!? Especially as LloydsTSB have a stoopid automated fraud protection thingy that automatically blocks my cards if they're used abroad.
And the most useful non-communication feature of the iPhone so far has been the built-in compass (I'd mistakenly assumed it needed a phone or wi-fi connection to work, but no). Kim has now taken on the role of map-reader.