Paul Reed's Great War Photos Blog:

The Library Time Machine: The Royal Borough of Kensington and Chelsea Library Blog:

The Great War Forum:

New Zealand History Online: New Zealand and the First World War

Australian War Memorial (Museum):

Peace Pledge Union:

British Postal Museum & Archive:

British Postal Museum & Archive: "Last Post: Remembering the First World War":

Archives of American Art, Smithsonian Institution:

Tate Britain/Tate Modern:

Imperial War Museum, London:

U.S. Library of Congress Digital Collections:

The Great War Archive:

The First World War Digital Poetry Archive:

The National Portrait Gallery:

Tommy's Pack Fillers (WWI reenactment supplies):

Google Books:

BBC History:

"For the King-Emperor: The Indian Army During the Edwardian and Georgian Eras, 1901-47":

"Participants from the Indian Subcontinent in the First World War":

British Empire and Commonwealth Museum and their related Images of Empire site:

PBS's "The Great War" 

The British Library:

"The Long, Long, Trail":