Public Domain Content

Multiple Media Types

Wikimedia Commons:
“A database of 4,909,797 freely usable media files to which anyone can contribute.”
http://commons.wikimedia.org/wiki/Main_Page

Creative Commons Search

Text

Project Gutenberg:
A database containing the text of over 30,000 (primarily public domain) books.
http://www.gutenberg.org/wiki/Main_Page

Images

U.S. Government Photos and Images:
Most, but not all of these, will be public domain. So check the license terms for the particular site you are in.

The Library of Congress has a Flickr site and “[a]lthough the Library of Congress does not grant or deny permission to use photos, the Library knows of no copyright restrictions on the publication, distribution, or re-use of these photos. “:
http://www.flickr.com/photos/library_of_congress/

Flickr – Creative Commons Search
Flickr Commons- Museums and Archives

Audio

1. CCmixter – Music

2. Freesound – Sound Effects

3. PDSound – Sound Effects

4. Sound Bible – Sound Effects

5. Public Domain Information Project – Music & Sheet music

6. Musopen

7. ibeat – free beats, loops & breaks

8. Free Music Archive – Music

9. Jamendo

Video

1. Entertainment Magazine’s Free Movies

2. Public Domain movies

3. Open Video Project

4. Internet Archive