In order to search for copyright-free images via Google:
- Go to Google.com, enter your search phrase, then click on "Images"
- On the upper right hand corner, click on the settings icon (circle with six knobs on it), and click on "Advanced Search"
- Under "narrow your results by..." find "usage rights" at the bottom of the list. Under "usage rights," select "free to use or share."

Copyright-free music is also available at http://www.jamendo.com and http://incompetech.com.

See the copyright-free material science sites (NASA, NOAA, Climate Interactive, etc.) in science resource discussion thread.