Social engineering resources. (http://packetstorm.decepticons.org/docs/social-engineering/)
NLP- powered social engineering. (http://online.securityfocus.com/guest/5044)
Social Engineering Fundamentals, Part I: Hacker Tactics. (http://online.securityfocus.com/infocus/1527)
Social Engineering Fundamentals, Part II: Combat Strategies. (http://online.securityfocus.com/infocus/1533)
CERT Advisory CA-1991-04 Social Engineering. (http://www.cert.org/advisories/CA-1991-04.html)
"Art of Deception," Kevin Mitnick (the king of social engineering).
Influence: The Psychology of Persuasion , by Robert Cialdini, Ph.D. Quill, 1998.
"The Milgram Experiment." http://www.new-life.net/milgram.htm and http://www.stanleymilgram.com/milgram.html.