Texas A&M University
Texas A&m University: Market Characteristics
This site sets up a list of market characteristics. Sample price and volume data included.
Other
Wright State U: Many Industries Are Congealing Into Lineup of Few Dominant Firms
This article examines the trend in many industries as mergers take place, leaving only a few dominant firms. As this changes, so does the role of government. (Published in the Wall Street Journal 03/08/1999)
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.