One can imagine the stacks of laws, court transcripts, weather data, declassified historical material, educational and propaganda films, music recordings, and so on that the richest country in the world has generated since it began in 1776. The fly in the ointment is that this material is not always easy to obtain. Consider this:
If you want to search federal court documents, it's not a problem. Just apply online for an account, and the government will issue you a user name and password.(From "Online Rebel Publishes Millions of Dollars in U.S. Court Records for Free"
Through the postal service.
And once you log in, the government's courthouse search engine known as Public Access to Court Electronic Records or PACER, will charge you 8 cents a page to read documents that are in the public domain — a fee that earned the federal judiciary $50 million in profits in 2006.
by Ryan Singe, Wired Magazine, 12/12/2008).
That is where a determined man can make a difference, and the man who stepped up is named Carl Malamud. Before and after setting up his organization, Public Resource, he accomplished a number of near-miracles:
Malamud has set up the nonprofit public.resource.org, headquartered in Sebastopol, California, to work for the publication of public domain information from local, state, and federal government agencies. Among his achievements have been digitizing 588 government films for the Internet Archive and YouTube, publishing a 5 million page crawl of the Government Printing Office, and persuading the state of Oregon to not assert copyright over its legislative statutes. He has also been active in challenging the state of California's copyright claims on state laws by publishing copies of the criminal, building, and plumbing codes online.(From the Wikipedia page on Carl Malamud).
The number of videos is now 6,005.
I have watched a few of the films that he made available on Public Resource's Youtube page and found a variety that includes German newsreels from World War II (like this), American ones (like this), a series of interviews on contemporary political science called "Conversations with History" (I enjoyed this one on Pakistan), an hour-long lesson from 2002 on using the Nikon D1 digital camera (here), and public health information (like these). If I were working on Social Studies projects, these would give background information and authentic footage that would give me a better mark.
Archive.org also has a wide variety of films, both short and long, that are out of copyright according to American rules. Malamud's collection, under the name "Fedflix," is here.
If you need photographs, rather than films, you can start your quest here, here, and here.