To add to your favorites, or bookmarks, depending on your choice of browser, right click on the link and select the appropriate "add to..." item.
Update: Dan Wood notified me that he modified this favelet to set the font color of highlighted text to black so that you wouldn't run the risk of white text on yellow or some other odd, hard to read color combination. Excellent idea, so I've made the change here as well. Ben Holt notified me that the favelet was changing the case of highlighted text, so I've fixed that. Thanks guys!
Update 2: Mihai Parparita has created a version of the Highlighter that will highlight your google search term on the document when it sees that google is the referrer. Very cool.