Despite great technological progress over the last few years, online translators (like Google Translate or Altavista BabelFish) should never be used as a primary tool for translation. Sure, they can help sometimes but should be used with extreme care and only if you have already ideas about how the good translation of a word should be. As advanced as a translation software is, it won’t be able to play with the subtleties of each expression, especially in their context.
This said, there is a great variety of tools available out there that can help you provide a quality translation (dictionaries, terminology databases, firefox extensions…). Some of them have been discussed in this topic. Don’t hesitate to recommend other tools!