HERE is a handy new feature for users of Google Talk that will help you with translating words on the fly.
The big G has incorporated translation tools into its service so if you want to translate a word from English to French, you invite en2fr@bot.talk.google.com to chat, then simply chat the line you want to see translated.
Of course any translation tool is only as good as the software driving it, so I wouldn’t rely upon it for important work, but if you use GMail and have chat enabled you could translate phrases received in an email.