World War 1
Worldwar1.com: Trenches on the Web: Introduction
Exhaustive site including everything you need to know about World War I. Includes numerous links and a reference library. Contains a long list of biographies from this period.
National Archives (UK)
National Archive: The Great War: 1914 1918
Students can examine original sources and how these have been used to support different viewpoints and perspectives on the Great War.