The Hyperwords Plugin
Hyperwords gives users a number of choices whenever a piece of text is selected. The options simply pop up – right click functionality remains unchanged.
Options include searching various engines, looking up text in wikipedia and dictionary.com, emailing text, searching on Google Maps, translation, and searching on Amazon and other commerce sites. The search and commerce traffic will generate revenue (my guess is a dollar or so per year per active user). The translation service is incredibly useful.