Public Domain
Works that are not restricted by copyright and do not require a license or fee to use. Works can enter the public domain automatically because they are not copyrightable, be designated in the public domain by the creator, or become part of the public domain because the copyright term has expired.
Below are a list of sites that offer public domain resources
Smithsonian Institution Public Domain Images
http://flickr.com/photos/smithsonian
New York Times Public Domain Archives
http://commons.wikimedia.org/wiki/Category:Public_Domain_Images_from_the...
Creative Commons Public Domain Images via flickr.com
http://search.creativecommons.org/
Search field: “public domain”
Select: “Search for works I can modify, adapt, or build upon.”
Select: flickr.com
Project Gutenberg
http://www.gutenberg.org/wiki/Main_Page
Librivox
http://librivox.org/
Internet Archive
http://www.archive.org/
Prelinger Archives
http://www.archive.org/details/prelinger
Creative Commons Public Domain films via blip.tv
http://search.creativecommons.org/
Search field: “public domain”
Select: “Search for works I can modify, adapt, or build upon.”