Have you been confused about the rules of copyright? If you are like me, you learn the rules, and then because you don't have to apply them for a while, you forget them.
If that is the case, this might be just the thing you need. Cornell University has created a reference guide that is easy to link to or store on your computer for handy reference. All of the different media and circumstances are presented in a single table that makes the myriad of rules fairly easy to negotiate.
You can see the guide at http://copyright.cornell.edu/resources/publicdomain.cfm