Open Source
There are tools and then there are tools. Resource that are free for all (for now). The mind boggles. Some cases in point:
The Internet Archive
The best media resource for me - ever! And the "Way Back Machine"!
Open Culture
Wonderful free cultural and educational media on the web
The Wikimedia movement
Just a few of:
The Public Domain Review
Also brings us: The Public Domain Image Archive
CCMixter
Music to use. A community music remixing site featuring remixes and samples licensed under Creative Commons licenses.