Many of the movies available for rent or purchase in the iTunes Store have built-in support for multiple languages for the audio track and subtitles, and you can switch among them while watching.
From the Inside iTunes website:
On the computer, move your pointer to produce the controls and click the speech balloon icon on the right (next to the airplay and full-screen icons) then select your language.
On the iPhone and iPod touch, the icon is also on the right in the control set; on the iPad, it’s on the left. And if you’re using any of those devices with AirPlay to stream what you’re watching via Apple TV, you can change the audio or subtitle language from your device as you watch.
If you’re playing the movie directly on Apple TV, press and hold the select button on your Apple TV remote, then navigate to the Subtitles and Audio tabs to choose the language you want.
You can also change the default audio and subtitle languages whenever they’re available for the movie you’re choosing. Choose Preferences from the iTunes menu on your computer and then go to the Playback tab to make the changes. On Apple TV, choose Settings, then Audio & Video and choose an Audio Language and Subtitle Language for each.
