And then there's Copyright

A copyright is a set of legal rights that an author has over his work for a limited period of time. Copyright covers everything from using images or sound files downloaded from the Web to photocopying.

Most information is protected by copyright. The exception is work that is in the "public domain, " which can be reproduced or used by anyone. However, you still must credit the author. Some examples of public domain sources:

Public Domain Sources	Examples
Publications of the U.S. Government		Government Printing Office Ben's Guide to Government (Has resources for K-12)
Copyright has been waived by the author		All Free Original Clip Art (1)
Works on which the copyright has expired		Works by William Shakespeare

1 Cartoons royalty free, provided by All Free Original Clip Art

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