Here’s a short post with a new Leopard treat I just happened on. You can select a word in your browser, email, document, just about anywhere. Then right-click and choose look up in dictionary. (Two other options let you search locally on your computer or network using Spotlight, or search the Internet using Google.)
After choosing “look up in dictionary” a pop up window is displayed with tabs for viewing a definition of the highlighted word, using the thesaurus to find a synonym or view the Wikipedia encyclopedia entry.
Here’s what it looks like in action . . .
View a brief tutorial on YouTube . . .