Creative Commons is a site that holds a huge amount of information. Much of it is legal in nature but there is a "search engine" that will allow you to do searches focused on free resources.
Content licensed under creative commons is free to use, reuse, share, modify and call your own. It was created by individuals who have chosen to share their content/material without any want of payment. In some cases the content can even be used for commercial projects.
The search engine allows you to search a number of different sites with creative common content. This can take some time but when using this engine you never have any questions about copyright or licensing.
Explore a little and see what you find.