Windows: Last year, Microsoft announced an app that would allow you to have real-time conversations with people who spoke different languages, built on Skype. While the service was only available to a small group of testers, it's now open to everyone.
The app currently supports translation between English, Spanish, Italian and Mandarin. Simply initiate a voice or video chat with your partner, and whatever you say will be transcribed and translated in real time. As with any translator app, it won't be perfect, but it can still break down the barrier in a way that hasn't been possible in the past.