I just used a feature of the NYTimes.com that i never knew existed before. As they explain in the footer of every article:

"To find reference information about the words used in this article, hold down the ALT key and click on any word, phrase or name. A new window will open with a dictionary definition or encyclopedia entry"

This reminds me of what Philip wrote in 2004 about "Context, Not Navigation": http://blogoscoped.com/archive/2004_05_25_index.html#108550924228985480