My colleague, Jeff Feinstein, who teaches US and European history, sent me this awesome link to the UK's National Archives. It deals with 20th century heroes and villains: Winston Churchill and the bombing of Dresden, John Kennedy and the Cuban Missile Crisis, Joseph Stalin and the industrialization of the USSR, Benito Mussolini and the invasion of Abyssinia, Harry Truman and the atomic bomb, Martin Luther King and the civil rights movement.
Click on each name and you'll find a treasure of sources, photographs, charts, graphs, and posters. The site's design is great and the sources for each individual are quite manageable for the kids.
I think that this site along with the curriculum sources from Stanford are among the best for their ease of use in the classroom.