Other
Egwald Web Services: Imperfect Competition Models: Differentiated Oligopoly
This site provides an in-depth study of a "differentiated oligopoly," and uses supporting graphs. For the advanced economics student.
Tutor2u
Tutor2u: Oligopoly
This site lists the characteristics of an oligopoly, and discusses price competition, non-price competition, and price leadership.
Other
South Western Learning: Oligopoly/monopolistic Competition: Kinked Demand Curve
This South-Western College Publishing website describes a situation in which oligopolistic firms vie for competition among consumers.