The Net is a fantastic place to find important historical works regarding the law and government, and those which get posted grow daily. Here are some places which post such works and I highly recommend your visit to these sites for a study of the documents and books posted there:

        I. Pre-Revolutionary:

Henry Sumner Maine's Ancient Law: Mr. Maine wrote many important works and this is one of them.

Frederic Bastiat's The Law: If you have not read this book, you should.

John Stuart Mill's Essay on Liberty: This work should be read by the serious student of liberty.

        II. America From the Revolution and After:

Thomas Paine's Common Sense: Paine was one of the major motivator's of the Revolution.

Collection of Historical Works from the Library of Congress: This site contains a huge collection of historical works.

The Making of America by the University of Michigan's Library: This site also contains a very large collection of important books.

Liberty Library of Constitutional Classics: Patriot Jon Roland has worked tirelessly to compile this enormous collection of important documents and books. You can get lost here.

The Avalon Project: Yale Law School has engaged in an effort to collect and post numerous works regarding the founding of this country.

Georgia Tech also has some historical works posted on its site.