I am a great lover of Creative Commons licensed content, and you may have noticed that all of my own content is Creative Commons licensed, so I am completely consistent. And I have written a few articles here on places that I have found that offer Creative Commons content. Now I am pleased to find that a search engine has been created to facilitate searching for and finding CC content. It is called Openverse, and it already indexes over 700 million creative works, so far consisting of stock photos, images, and audio content. Sources include the Smithsonian, the Cleveland Museum of Art, NASA, Flickr, Europeana, and the New York Public Library. But they are looking to expand both the sources they index and the types of content. You can see more about some of the sources they index at https://openverse.org/sources. They estimate that there are 2.5 billion CC-licensed items of all types, and they plan to eventually include texts, 3-D Models, and more.
Openverse is the latest incarnation of CC Search, which was developed by Creative Commons, and then adopted by WordPress. They are looking for contributors, of course, like most projects.