Lingoo is an application wrapper for the Google Translation online service. The program is implemented as an background application hiding in the Menu bar with few hotkeys to activate the translation when it is needed. This tool contains a number of preferences to simplify the usage: it can run at login, it can automatically select the translated text or put it into the Clipboard, it can read Clipboard data when called and immediately translate it with languages autodetection, and it can also select the destination language depending on the source.
One World Dictionary by Ascendo is a leading multilingual reference tool for Apple desktops.
InstantTranslate makes it really easy to translate a selection of text in the application you are working in from one language to another language.
