Just as a note from someone who has rendered a few graphics over the years :) -- the Internet is not public domain. Be very careful that you are not infringing on anyone's copyright, as this has the potential of leading to negative consequences. For example, having your video removed from Youtube.
That being said, feel free to share your resources for finding royalty free graphics and videos.
Aloha and what an important reminder! I wanted to share this great site that I've used for FREE royalty-free stock images for my book trailer. I do caution about using some of the model images, there are beautiful ones, but read the licensing on them carefully. A few do NOT have model releases signed or on file. While it may be their face and image, the image may also be owned by the photographer who took the photograph, so as with any resource always use due diligence and proceed with caution :)