http://www.grolier.com/presidents/ea/side/impeach.html
The definition of "Impeachment" in the Encyclopedia Americana, including
concise introduction to the origin of impeachment, the process and
problems of American impeachment, and the impeachment cases of Nixon and
Andrew Johnson.
http://www.infoplease.com/ipa/A0764613.html
A brief history of impeachment, including a very clear and concise
description of the impeachment mechanism, and explains what are "High
Crimes and Misdemeanors"
http://www.essential.org/books/impeach/
The Citizen's Guide to Impeachment, organized by FAQs about "Impeachment".
A very comprehensive and easy-to-understand guide to impeachment.
http://www.lawschool.cornell.edu/lawlibrary/subjects/fedimp/fedimptc.html
A bibliographic guide to English and American precedence, historical and
procedural development, and scholarly commentary, including impeachment
provisions of the US constitution, impeachment precedence, impeachment
procedure, etc.
http://vh1337.infi.net/special/impeach/html/c.htm
A summery of the impeachemnts against Andrew Johnson, Richard Nixon and
Bill Clinton, including their terms, accusation, the congress' action and
the result.