You can find OER resources in Google by using the Advanced Search feature.
1. Input your search terms and get your results list
2. Click on Settings and choose Advance Search
3. Scroll down to "Usage Rights" and choose the license level you need
BING IMAGE search offers a License Filter
1. Click on your search terms
2. Just above image results, you will find filter choices: Image Size, Color, Type, Layout, People, Date, and License.
YouTube Filters find videos which have Creative Commons licenses for legal use.
1. Input your search terms.
2. Click on "FILTER".
3. Under "FEATURES" choose Creative Commons