Some sources for images to liven up your presentations or papers.
Google Images Use the advance search to filter by filetypes, usage rights, and more. Search historic images from the LIFE photo archive by adding "source:life" to any Google image search.
ARTStor is a digital library of over one million images in the areas of art, architecture, the humanities, and social sciences with a set of tools to view, present, and manage images for research and pedagogical purposes. Use Internet Explorer.
Flickr Users around the world share and organize images via Flickr. The website now hosts over three billion images.