What's Copyrighted?

Before trying to determine what copyrighted works can be used - how much, under what conditions, for what purpose and for how long - take a moment to figure out whether the work you wish to use is even protected by copyright in the first place.  If it isn't, for example if the copyright has expired, then there would be no copyright concerns regarding your proposed use.

Knowing some basic copyright information is a good place to start.  Find out what the public domain is and how to check the public domain status of the work you wish to use.  There is a wealth of helpful information on the web, including copyright tutorials and very rich copyright websites.