Annenberg Foundation
Annenberg Learner: Economics U$a: 21st Century Edition
A micro and macroeconomics course for 21st century learners. 28 half-hour videos sessions with text and guides regarding markets, firms, supply and demand, perfect competition and inelastic demand, economic efficiency, monopolies,...
Robert Schenk, PhD
Cyber Economics: The Theory of Few Sellers
An overview of monopoly, oligopoly and duopoly, focusing on the interdependence of firms in an oligopoly, shown through the use of a game tree how these firms are tempted towards the practice of collusion.
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.
Other
Elemental Economics: Review of Basic Definitions: Competition
This site provides a good description of the four types of market structures: perfect competition, monopolistic competition, oligopoly, and monopoly, along with the major characteristics of each.
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.