The Holocaust (HaShoah, in Hebrew) refers to the systematic murder of more than six million Jews orchestrated by Adolph Hitler and the National Socialist (Nazi) Party in Europe during World War II.

 The Holocaust according to Wikipedia

The University of Southern Califorinia Shoah Foundation
I witness - an online application that gives educators and students access to more than 1,000 video testimonies of Holocaust survivors and other witnesses

The United States Holocaust Memorial Museum
A living memorial to the Holocaust, the United States Holocaust Memorial Museum inspires citizens and leaders worldwide to confront hatred, prevent genocide, and promote human dignity. Federal support guarantees the Museum's permanent place on the National Mall, and its far-reaching educational programs and global impact are made possible by generous donors. 
  Holocaust encylopedia