About online dictionaries at your fingertips. Jackie told everyone about this eons ago and I've been using it ever since. Atomica (formerly Gurunet) is a great online program that functions as a dictionary (it uses American Heritage), thesaurus, encyclopedia, almanac, history book, search engine, translator, weather ticker, atlas, medical and science dictionary, and wondrous other reference materials. All you have to do is download it at http://www.atomica.com (it's completely free), install it and then you just alt+click on any word in any document on your computer. It will automatically pop up and give you info about the word, term, person, place etc as long as you have the internet on when you want to use it.

Excuse me for sounding like an advertisement, but I think this thing is great.