Britannica Online :  A good place to start your search for basic information. 
Gilder Lehrman Institute Module on the Constitution--Click on the Learn more about the history and meaning of the Constitution and follow the links in the popup.

Charters of Freedom: This site has detailed explanations and history of The Declaration of Independence, The Constitution and The Bill of Rights. The links offer biographies of the delegates and a list of questions and answers about the constitution.

A Roadmap to the U.S. Constitution: Details the issues, creation, origins, and cases of the Constitution.

Ben's Guide to U.S. Government--Learn about the writing of the Constitution and link to Constitution trivia.  There are many other topics here, too.

Amendments Not Ratified: During the course of our history, in addition to the 27 amendments that have been ratified by the required three-fourths of the States, six other amendments have been submitted to the States but have not been ratified by them.

 Thomas Federalist Papers:  Browse the papers, learn who wrote what, when and where.

The Signers of the Constitution: Biographical sketches of the signers of the constitution.

American National Biography :Over 17,000 people whose lives have shaped our history.  Use the quick search by name at the top of the page.

Distinguishing Federalists and Antifederalists:  Description of a lesson plan with links to other sites and information on the Federalists.

Landmark Supreme Court Cases: This site contains summaries of cases and excerpts opinions. Click on the cases listed along the left side of the page. You'll find a diagram of how the case moved through the court system. Listen to the oral arguments.

Milestone Cases in Supreme Court History: A short summary of 6 historic cases.

OYEZ U.S Supreme Court Multimedia  Click on cases and then search by subject to get a abstract of the case and the voting.  If you have problems finds you case scroll down to the bottom of the page and click on Most Popular Cases.  Look for your case.
Full Text of Supreme Court Cases--Cases are listed in chronological order.