If you are looking for images to use in academic projects or web sites, be sure to be aware of licensing and copyright issues. Below are a number of resources to help you find free-to-use or Creative Commons licensed images.
Search Creative Commons
“Please note that search.creativecommons.org is not a search engine, but rather offers convenient access to search services provided by other independent organizations. CC has no control over the results that are returned. Do not assume that the results displayed in this search portal are under a CC license. You should always verify that the work is actually under a CC license by following the link.”
Flickr Advanced Image Search
Although Flickr is searched by “Search Creative Commons” above, CB Creative Bloq helpfully advises that you can do a more in depth search here and can save a library of links to your favorites.
Google Advanced Image Search
Wikimedia’s “Free Image Resources” Page
Overwhelming number of resources listed here. Let me know (firstname.lastname@example.org) if you find any particularly useful.
“The Internet Archive, a 501(c)(3) non-profit, is building a digital library of Internet sites and other cultural artifacts in digital form. Like a paper library, we provide free access to researchers, historians, scholars, the print disabled, and the general public.”