Pond5 hosts a huge repository of video, images, audio clips, and 3D renderings. They also have a paid section. Follow the link below for a huge amount of public domain content.
“Whether you’re a filmmaker, musician, designer, student, or just a history buff, the Pond5 Public Domain Project is making copyright-free media available for you. You’ve got stories, and we’d love to help you tell them.
Utilize the history of man as told through cameras, microphones, and more–expertly prepared and optimized for the media makers of today.”