LibGuides: Copyright Basics: Public Domain Resources

Definition of Public Domain

Public Domain definition from Public Domain Sherpa

Put simply, the public domain consists of works that aren’t protected by copyright or by other legal means. You are free to use public domain works however you wish, without seeking permission, because ...

their copyrights have expired; or
the copyright owner didn’t follow certain required formalities (so they didn’t get a valid copyright); or
the works weren’t eligible for copyright in the first place; or
their creators dedicated them to the public domain.

http://www.publicdomainsherpa.com/definition-of-public-domain.html

Public Domain Resources

Digital Public Library of America
DPLA connects people to the riches held within America’s libraries, archives, museums, and other cultural heritage institutions. All of the materials found through DPLA—photographs, books, maps, news footage, oral histories, personal letters, museum objects, artwork, government documents, and so much more—are free and immediately available in digital format.
Duke University Center for the Study of the Public Domain
The Center for the Study of the Public Domain at Duke Law School is the first university center in the world devoted to the other side of the picture. Founded in September of 2002, as part of the school's wider intellectual property program, its mission is to promote research and scholarship on the contributions of the public domain to speech, culture, science and innovation, to promote debate about the balance needed in our intellectual property system and to translate academic research into public policy solutions.
Library of Congress
Wonderful resource for all things American and more – a huge collection of print, pictorial and audio-visual material. Most of the material is public domain but not all so do check on a case by case basis. Use the search bar in the top right or navigate via their very interesting curated collections.
Librivox
LibriVox volunteers record chapters of books in the public domain, and then we release the audio files back onto the net for free. All our audio is in the public domain, so you may use it for whatever purpose you wish.
New York Public Library Public Domain Images Visual Browsing Tool
On January 6th, 2016, The New York Public Library made over 187K digital items in the public domain available for high resolution download. This is one of many experiments by the NYPL Labs to help patrons understand and explore what was contained in that release.
Prelinger Archives
Prelinger Archives was founded in 1983 by Rick Prelinger in New York City. Over the next twenty years, it grew into a collection of over 60,000 "ephemeral" (advertising, educational, industrial, and amateur) films.
Project Gutenberg Project Gutenberg offers over 57,000 free eBooks. Choose among free epub books, free kindle books, download them or read them online. You will find the world's great literature here, with focus on older works for which copyright has expired. Thousands of volunteers digitized and diligently proofread the eBooks, for enjoyment and education.
Public Domain Review
Founded in 2011, The Public Domain Review is an online journal and not-for-profit project dedicated to the exploration of curious and compelling works from the history of art, literature, and ideas.
Smithsonian Public Domain Images on Flickr
A collection of 6,288 images from smithsonianimages.si.edu which appear to be overwhelmingly in the public domain.