Google just began offering instant machine translations for Google Talk and Gmail.

You can access the new service from within Google Talk, the chat window in Gmail or any IM client that supports the Jabber protocol. To use the service, add these addresses as friends en2es@bot.talk.google.com for English to Spanish translations, or es2en@bot.talk.google.com for Spanish to English translations.

You can also add the robot to a group chat and let it translate between the two of you on the fly. Here is a complete list of languages and their codes that are available.

The translations are far from perfect, as you can see from the following dialog.

David: How good are translations when you use machine translation software?
en2es: ¿Cómo son buenas traducciones cuando utilice programas de traducción automática?

The translation probably should have been something like this: ¿Qué tan buenas son las traducciones cuando usas programas de traducción automática?

When translating from Spanish to English, you need to use all the correct punctuation marks and diacriticals to help it guess the right meaning.

David: Buenos dias como estas?
es2en: Hello like this?
David: Buenos días, ¿cómo estás?
es2en: Good morning, how are you?