Interactive US Constitution from the National Constitution Center
The US Constitution from the National Archives
The Declaration of Independence
The Role of the Supreme Court
Marbury v. Madison:
http://www.ourdocuments.gov/doc.php?flash=true&doc=19
http://www.pbs.org/wnet/supremecourt/democracy/landmark_marbury.html
McCulloch v. Maryland:
http://www.ourdocuments.gov/doc.php?flash=true&doc=21
http://www.pbs.org/wnet/supremecourt/antebellum/landmark_mcculloch.html