Economics: Principles, Problems, and Policies. 12th Ed. McConnell, Campbell R. and Stanley L. Brue. McGraw-Hill, Inc. New York.1993.
Provded information on how monopolies affect the economy, and gave graphs to illustrate trends.

Free to Choose. Milton & Rose Friedman. Harcourt Brace Jovanovich. (c) 1980.
Showed economic trends, and that monopolies were one of those trends.

Monopoly and Microsoft. Corporate Watch. 2 July 1998.
http://www.igc.apc.org/trac/feature/microsoft/monopoly/
Gave examples of past monopolies, and why Microsoft fit the description.

http://www.newsweek.com
Several articles on the Microsoft Anti Trust, and what Microsoft can do to get out of it, or why it isn't a monopoly.

Microsoft Antitrust is a Farce
Argues that the ongoing antitrust against Microsoft is unfounded.

http://www.smart.net/~kaz/inframe/microsoft.html
Argues that Microsoft isn't a monopoly, and that it's compatition were larger monopolies in their day. Significant holes in his arguments.

Principles of Economics. N. Gregory Mankiw. The Dryden Press. (c) 1998.
Provides more trends of monopolies, has graphs that demonstate this very well. Does a very good job of explaining complex economic issues simply.