Smithsonian Magazine: Hell's Bells - Includes several articles on labor conditions in the 19th century. - http://www.smithsonianmag.com/issues/2002/may/object.php
Child Labour 1750-1850 - Extensive treatment of the topic, from the Encyclopaedia of British History. - http://www.spartacus.schoolnet.co.uk/IRchild.main.htm
Labor Arts - Virtual museum exhibiting and cataloging the art of the labor movement and working people. Collections include parades, cartoon art on labor themes, and buttons and badges. - http://www.laborarts.org/