Do a websearch for listings of works in "the public domain".

Might also want to use the search engine to find out about Public Domain and copyright law.

For all questions pertaining to copyright in the US, the US Copyright Office has a webpage with a really good FAQ page and should be your first source for info concerning Copyright issues:

http://www.copyright.gov/

Trust no other source.

Stories about copyright are often wrong. Many do not seem to want to take the time to understand copyright issues or perhaps are willfully trying to ignore or otherwise contribute a good bit of nontruth and confusion to the issue.

--Mac