Elbert found this:
The Yahoo Translating Proxy works with Yahoo! Messenger to translate your typed message into various languages. This Yahoo Translating HTTP Proxy (YTP) is a two-way translator which works with your Yahoo! Messenger to translate your typed message into various languages. Your friend will receive translated message, and she can type back in the translated language. For example, if you type to her in English, she can receive the message in French. She can then type back in French and you will get the message in English. The following languages are supported:
English -> German, Spanish, French, Italian, Portuguese
German, French, Spanish, Italian, Portuguese -> English
French -> German
German -> French
Link to page:
http://choicelearning.blogspot.com/2006/01/two-way-language-translator-for-yahoo.html