Memorust is an application to help you build a vocabulary in any language. It has a full UNICODE support which means that you can learn languages with specific characters like Czech, Russian, Chinese and all others that Mac OS X supports.
InstantTranslate makes it really easy to translate a selection of text in the application you are working in from one language to another language.
One World Dictionary by Ascendo is a leading multilingual reference tool for Apple desktops.
