Many people are familiar with Wikipedia, the online open encyclopedia. However, Wikipedia is just one component of a larger Wikimedia world. One of my favorite tools for students to use for creation is Wikimedia Commons. This is a repository of images, sound, video, and more that is free for users to use and share (with very limited licensing restrictions).
Materially hosted on Wikimedia is under an open content license. This means that users can reuse the material without contacting the creating, but:
some licenses require that the original creator be attributed,
some licenses require that the specific licence be identified when reusing (including, in some cases, stating or linking to the terms of the license), and
some licenses require that if you modify the work, your modifications must also be similarly freely licensed.
If you have your students create videos, presentations, websites, or more, this is a great place for them to learn about copyright law and licensing restriction without fear of unwittingly violating the law.