Download from Flickr (4:48)
Smithsonian Institution Research Information System - A searchable treasure trove of photographs, videos, images, and more.
Photopin - Offers an easy way to search Creative Commons images and are easy to download. Generates a code you can embed crediting the photo owner automatically!
Google Images - Another image search engine. Use the Advanced search for finding copyright-free images. Harder to make the CC determination here.
Yahoo Images - Yahoo now owns Flickr but retains its own search engine for finding CC images.
The Commons - A gathering of the world's public photography archives, a cooperative effort between Flickr and the Library of Congress.
Slideshare - A source for presentation slides done by others and then shared. Some presentations are from academia, the business world and students for assignments. While the slides can't be copied directly, you can find images you like then locate them using their source information.
The Health Education Assets Library (HEAL) is a digital library that provides freely accessible digital teaching materials of the highest quality that meet the needs of today's health sciences educators and learners.
The collection includes portraits, photographs, caricatures, genre scenes, posters, and graphic art illustrating the social and historical aspects of medicine dated from the 15th to 21st century.