TED-Ed allows you to modify any of their videos, or any of the videos on YouTube (which include Khan Academy) through their website.
What you can add: Title, introduction/instructions, quiz questions, short answer questions, additional information/resources.
How do you do it:
- Go to http://ed.ted.com/
- Find a video through the website, or through their “YouTube” tab and open it up.
- Find the “Flip” box near the video and start adding information.
- They will give you a link to share with your students once you have finished.
Additionally: You can have students login and you may track their progress.