Usually, I have to communicate with the people in the building's management office via Google Translate. It works, but it's awfully painful to be constantly flipping the language drop-downs back and forth. (It's two drop-downs, one for source and one for target language.)
So I wrote a little javascript gadget that does the hard work for me, and also keeps a “log” of the conversation. You can peruse it at http://lalomartins.info/transchat.html
(Attention though: this is not a chat app, not in the modern sense. It's “chat” in the old-school sense, of actually talking to a person that's in front of you. It's... an interpreter widget, not a chatbox :-) enjoy and spread if you wish...)