Google Images - There is a subset of pictures on Google Images which are under Creative Commons. To find them, first use a search term within images.google.com then narrow your search by clicking:
Tools -- Usage Rights -- Creative Commons Licenses
Creative Commons search
Flickr - To find the copyright free images, use a search term to find photos on your subject, then use the drop down menu under “Any License†to choose “creative commons†or “modifications allowedâ€
PhotosForClass.com (free for educators and students)
Library of Congress Free-To-Use Sets
New York Public Library Digital Collections - must look under the image to determine the usage restrictions
Metropolitan Museum of Art Open Access Collection
PublicDomainPictures
- choose the free download option under the photo