A brief history of computing
Timeline: Chronology of the History of Computing
The History of Computing Project
http://www.thocp.net/timeline/timeline.htm
The Modern History of Computing
B. Jack Copeland
http://plato.stanford.edu/entries/computing-history/
An Illustrated History of Computers
John Kopplin
http://www.computersciencelab.com/ComputerHistory/History.htm
The Babbage Engine
Computer History Museum (Mountain View, California, USA)
http://www.computerhistory.org/babbage/
The Hollerith Machine
United States Census Bureau
https://www.census.gov/history/www/innovations/technology/the_hollerith_tabulator.html
Timeline - CHM Revolution
Computer History Museum (Mountain View, California, USA)
http://www.computerhistory.org/revolution/timeline