To limit all of your searches to open access materials click on the left side of the Open Access filter at the top left of your search. This will turn on a lock. This limit will now last for your entire search session.
Use the Advanced Search on Google to find Creative Commons material.
Find the 'usage rights' filter and select 'Free to use, share, or modify'. Enter your search term and run the search.
This will return things under any CC license. If you wish to use the resource commercially, please select an appropriate option.
To find Creative Commons licensed videos on YouTube run your search first.
On the results page click Filters (just above the first result) and select 'Creative Commons' under the heading 'Features'. Similar to the Advanced Google Search, it will show all videos under the CC license and so the license of the video will have to be checked before use.
Use the Creative Commons meta search tool CC Search to search for a wide range of openly licensed images, audio and videos: