Internet History Sourcebooks Project
Fordham University: Modern History Sourcebook: German Invasion of 1941
This site from the Fordham University provides an address by Vyacheslav Molotov, Foreign Minister of the Soviet Union, containing the Soviet reaction to Germany's invasion.
BBC
Bbc History: World Wars: World War Two: Hitler's Invasion of Russia
Five-part article in which Hitler's reasons for invading Russia are explained and considered.