If you’re looking for free clip-art, free stock photos, free music, free articles, you can make use of Google’s “Usage Rights” search.
This little-known search feature is found on Google’s Advanced Search page, and lets you specify what kind of content you wish to find, according to whether it’s free to use or share, whether its free to modify, and whether it’s free even for commercial use.
As Google’s Usage Rights help page explains, Google is selecting the results based on links back from the content website to the free-licensing site Creative Commons. This alone doesn’t guarantee that every search result returned will be free to use. You will still need to double-check the item you wish to use, but those search results will be the best place to start looking.