The U.S Supreme Court
Landmark Cases of the Supreme Court
http://www.landmarkcases.org/

The Avalon Project at Yale: Documents in Law, History and Diplomacy
http://avalon.law.yale.edu/default.asp

The Supreme Court of the United States
http://www.supremecourtus.gov/

Oyez: U.S. Supreme Court Media (current events)
http://www.oyez.org/
New site: http://us.oyez.org/

The Supreme Court Historical Society
http://www.supremecourthistory.org/

Good place to start!
Search for you case here...