The Library of Congress is an amazing resource. It is the largest library in the world and has put much of their collection online.
What is available? "Spoken history, photographs, and iconic cultural resources are available as teaching resources, and many of them are neatly organized into lesson plans, collections, and themes, perfect for bringing them into the classroom."
Since searching for the resources may be "overwhelming" this post provides "a short guide to making the most of the Library of Congress, with tips and ideas for activities, plus links to guides, resources, and tools that you can put to work in your classroom."
Via Beth Dichter