eLEOquent provides you with quick access to a bidirectional English-German dictionary, as well as a French-German one, through the system-wide Services menu and keyboard shortcuts respectively. What this means is that you can easily look up a word translation for the current text selection - without the hassle of copying it to the clipboard at first, activating eLEOquent then, pasting the text there and eventually starting the search. Even though you can also interact with eLEOquent in this way if you want to, of course.
Mac OS X 10.4 PPC
Mac OS X 10.4 Intel
||Mac OS X 10.4.3 or laterUniversal Binary