Flickr contains millions of photographs shared by Flickr users under Creative Commons licenses, and is a strong source for contemporary travel, nature, people, and design photographs.

 Find Creative Commons images in Flickr  (2:14)

 Download from Flickr  (4:48)

Several overlays to Flickr offer enhanced search functionality and additional features:

• Flickr Creative Commons: Flickr's Creative Commons portal. Browse by license type or choose "Advanced Search" to limit to Creative Commons content.

• The Commons by Flickr: Public photo archives, from the New York Public Library, Smithsonian, Library of Congress, Getty Research Institute, and more. The images have no known copyright restrictions.

• Wylio: Searches only Creative Commons content in Flickr. Includes resizing tool, photo credit builder, and code generator. Requires account.
• PhotoPin: Search millions of Creative Commons photos from Flickr; good source for blog images.

• Internet Archive Book Images -- Over 2 million images from historic, out-of-copyright books. Find out more.
• The British Library's Flickr Stream - Over 1 million images from 17th, 18th, and 19th century books. Anyone can use, remix and repurpose! Example: The British Library Meets Burning Man

Google's Image Search has a usage rights filter on the Advanced Search and Advanced Image Search pages shows  pages that are either labeled with a Creative Commons license or labeled as being in the public domain. 

 How to filter Google Images by Usage Rights  (0:49)

ArtStor -- a great source of high quality images, but not copyright-free. See their Images for Academic Publishing for images that can be used for classes and other academic publishing..

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The following sites are great sources of copyright-free images:

• Search for Creative Commons (images, films, musics, etc.)

• Getty Open Content: Public domain art images from Getty collections.
   
• Images by Subject -- Links to image sources by subject (art, history, science, etc.), not neccesarily copyright-free. (University of Washington Libraries).
   

• Library of Congress Prints & Photographs Online: Images from the Library of Congress, now in the public domain.

• NGA Images - National Gallery of Art: Includes more than 20,000 open access digital images, available free of charge for download and use

• Sonoma Heritage Collections  - Extensive links to Sonoma County historical photographs, maps, and more.
   
• Yahoo Images - Yahoo now owns Flickr but retains its own search engine for finding CC images.
   
• Yale Photogrammar -- 170,000 photographs from 1935 to 1945 created by the United State’s Farm Security Administration and Office of War Information. Search by county, date, subject, photographer. Includes 170 photos from Sonoma County, especially poultry and wine industries. Copyright-free.

• Wikimedia Commons: Historical and contemporary images contributed by participants. Millions of high-resolution images of art, architecture, design, people, historical events, diagrams, maps, and more.

• WorldImages - From California State University, a collection of approximately 80,000 images which is global in coverage and includes all areas of visual imagery.

See also Online Archives and Museums

[Image: Hawk Owl, via Public Domain Clip Art]

• Corbis Royalty Free Images: This selection of Corbis images may be used for commercial and non-commercial use, free of charge

• Compfight: Enhanced search of Flickr content. Limit to Creative Commons.

• MorgueFile Free Photos: Public image archive for creative work

• Image*After: Large collection of free stock images and textures that may be modified and re-used for personal and commercial projects

• stock.XCHNG: Free stock images, powered by Getty Images

• Clip Art History: Free high-quality public-domain clipart covering all ages of world history. Images may be used for any purpose

• Public Domain Clip Art: Large collection of public domain clip art. Images may be used for any purpose and registration is not required