Authors can choose one of six different license conditions, covering the spectrum of possibilities between full copyright (all rights reserved) and the public domain (no rights reserved).
There are hundreds of millions of works — from songs and videos to scientific and academic material — available to the public for free and legal use under the terms of Creative Commons copyright licenses, with more being contributed every day. Creative Commons materials can be used, not only in your academic life, but anytime you need to use a preexisting piece of information without worrying about copyright infringement.
Find CC Material on the Creative Commons site.
Flickr: Creative Commons --contains many cc licensed photos
ccMixter --contains many cc licensed music mixes
Jamendo --another platform for cc licensed music
Freesound--provides cc licensed sound samples
Youtube --how to access and/or upload cc videos on youtube