This is pretty cool, I miss clicked and found a new feature in Word 2003. Hold down ALT and click on a word. The Research bar comes up with the definition, thesaurus, and a translation for the word you clicked on.
This is even cooler! If you click on translate, it takes you to WorldLingo.com and shows you a translated version of your document in the language of your choice.
I do have my gripes with Office, but this is pretty darn cool!