Creative Commons presents cultural, scientific and other works released as CC. In most cases you have to attribute credit to the artist that created the work, but the requirements vary.
Archive.org has public domain or creative commons licensed music, images, video, live recordings, texts. Everything on the site has the specification for how it can be used and which type of license it has.
The Library of Congress, especially the digital collection has wonderful historic photos, maps and recordings that “we the people” own.