Public Domain Media From the U.S. Government
Most media produced my the U.S. Government is in the public domain, with a few exceptions that were produced by outside producers.
Please note that people pictured in the media my still retain their publicity rights. For example, it might be legal to use a NASA video clip of an astronaut in an educational film, but to use the same clip in a commercial would likely violate the astronaut’s publicity rights.
Works created by state and local governments do not automatically fall into the public domain. Also U.S. government created works may fall under copyright protection outside of the US. For more information on U.S. Government copyrights, look here: https://www.usa.gov/government-works
DVIDS
The DVIDS (Defense Video & Imagery Distribution System) provides up-to-date video, audio and images of ongoing military operations.
According to their website, “The DVIDS mission is to serve as a turnkey operation that facilitates requests for Public Affairs video, audio, still imagery and print products; coordinates interviews with soldiers and commanders in a combat zone and provides an archive for ongoing operations in Iraq, Afghanistan, Kuwait, Qatar and Bahrain.”
NOAA Photo Library
The NOAA Photo Library has a large collection of photos including coastlines, coral reefs, animals, oceans, fisheries, weather and more. Almost all of the photos are in the public domain, the few that are under copyright protection will be noted as such in their caption.
NOAA National Marine Sanctuaries Media Library
https://marinelife.noaa.gov/media_lib/
NASA Image Galleries
https://www.nasa.gov/multimedia/imagegallery/index.html
NASA Curiosity Image Gallery
The view from Mars
http://www.nasa.gov/mission_pages/msl/multimedia/gallery-indexEvents.html#.VrDmB7IrKHs
USDA NRCS Photo Gallery
http://photogallery.nrcs.usda.gov/res/sites/photogallery/
USDA ARS (Agricultural Research Service) Photo Gallery
http://www.ars.usda.gov/News/docs.htm?docid=23559