Copyright is the ownership of an intellectual property within the limits prescribed by a particular nation's or international law. In the United States, for example, the copyright law provides that the owner of a property has the exclusive right to print, distribute, and copy the work, and permission must be obtained by anyone else to reuse the work in these ways. Copyright is provided automatically to the author of any original work covered by the law as soon as the work is created. The author does not have to formally register the work, although registration makes the copyright more visible.
Copyright for Teachers and School Librarians - http://users.mhc.edu/facultystaff/awalter/Brim%20site/index.html
Creative Commons is a non-profit organization that was formed to allow artist to allow use of their works under certain conditions. In most cases work under a Creative Commons license can be used for free as long as the artist or musician is given credit. Here are some resources that can be used in video or powerpoint presentations under the Creative Commons license.
http://wiki.creativecommons.org/Marking/Users - How to give credit using CC guidelines.
http://www.jamendo.com/ - Royalty free music for documentaries, movies, and web videos.
http://www.flickr.com/creativecommons/ - Flickr allows users to use CC licenses for their work. You may use these pictures under the stipulations of the license.