The Raspberry Pi is a remarkably capable portable computer that constantly surprises us. Dave Conroy found a use for it we couldn't have imagined: he turned his into a translation device capable of translating over 60 languages. It supports speech recognition and playback, and the whole task is all done with free software.
You'll need a persistent internet connection, since it uses Google's text-to-speech engine to work and Microsoft's translation engine (since access to Google Translate's API is $20, and he wanted to do it all for free). Conroy used a Logitech USB headset to make it all work (any other model should be OK provided you can find suitable drivers). Hit the link for the full construction details.