Many public domain images and content can be used without attribution. You can also purchase stock photos you do not have to attribute. This may be useful for designing presentation title slides, digital badges, logos, or book covers. You can add a link at the end to show where you got the resource.
Millions share their work for anyone to use, but require proper attribution and ways to use that work! They outline these details in a Creative Commons (CC) license. Find out more at CreativeCommons.org.
Read the CC license of content carefully to see if you can redistribute them, use for commercial purposes, or change/edit the content. Not all CC content allows you to do this, which means you may not be able to share your remixed creation with others.
Find CC licensed images and video clips on Flickr and Wikimedia Commons. Find more sources for images in the bookmarks below!
Compfight is a search engine and my favorite way of finding Flickr content to use.