All images and videos on Pixabay are released free of copyrights under Creative Commons CC0. You may download, modify, distribute, and use them royalty free for anything you like, even in commercial applications. Attribution is not required.
Wikimedia Commons is a media file repository that is completely dedicated to providing educational media that are released either in the public domain or under Creative Commons license. Search tip: To check the license information on any image, scroll down the page to the Licensing section.
Flickr hosts millions of Creative Commons-licensed images. Notably, Flickr provides a separate Creative Commons licensed videos collection. Search tip: After searching with a keyword, click the "Any license" filter to narrow down to images with different kinds of open licenses.
The Unsplash license uses the Creative Commons Zero license, which doesn’t require credit to be given. However, they encourage giving credit to the photographer if possible, since they generously donated their photographs for use by the public.
Morguefile is a free photo archive. The site was created to serve as a free image exchange for creative professionals and teachers to use in their work. Search Tip: Search by keyword and then click on the license link for more specific info on how to use that image.
TED Videos are not officially licensed with any kind of open licensing. However, TED allows the users to freely view and download the videos without restraint. The website is provided as a public service to promote the spread of good ideas.
Khan Academy provides top-quality educational videos that are organized by discipline and skill levels. They provide videos from various disciplines including Math, Science, Economics, Finance, and Humanities.
iTunes U is a vast learning resource offering free educational content that users can download from Apple's iTunes Store straight to their computer or mobile devices. The Open University joined iTunes U in 2008, making available a range of high quality audio-visual assets used in their courses.