These websites contain good quality, relatively clear, information on the topics of copyright and fair use:

Copyright Bay
      Designed for educators, but also useful for older students. Copyright and fair use are covered.

Copyright Kids
       Don't be fooled by the name; this interactive site is quite detailed and comprehensive.

10 Big Myths About Copyright Explained
    Highly recommended.

Copyright Basics       
    From the University of Michigan; this brief overview contains some information not covered on the other sites. Also links to more complex detailed information.

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ICLIPART.com
    This site contains royalty free images, including animated images, thought to be available for unrestricted reuse. The site attests, "To the best of our knowledge, all of the clip art images available here are in the public domain and can be freely used by anyone. If you have evidence suggesting that one or more of the images existing on this server is copyrighted then please e-mail us the details and we will remove them immediately."