Lichan Hong, Ed H. Chi, Raluca Budiu, Peter Pirolli, and Les Nelson, SparTag.us: Low Cost Tagging System for Foraging of Web Content, in Proceedings of the Advanced Visual Interface (AVI2008), pp. 65-72, ACM Press, 2008. (pdf)

"We introduce a new tagging system called SparTag.us, which uses an intuitive Click2Tag technique to provide in situ, low cost tagging of web content. In SparTag.us, we bring the tagging capability into the same browser window displaying the web page being read. When a user loads a web page in his browser, we augment the HTML page with AJAX code to make the paragraphs of the web pages as well as the words of the paragraphs live and clickable. As users read a paragraph, they can simply click on any words in the paragraph to tag it."

Via Augmented Social Cognition