OpenPhoto, http://openphoto.net/ - an example of a photocommunity offering a collection of "hundreds of stock photos" licensed for commercial and non-commercial use.
Pics4Learning, http://pics.tech4learning.com/ - a copyright friendly image library designed for use in educational settings. Its thousands of images were donated by students, teachers, and amateur photographers.
The Open Clip Art Library: Drawing Together, www.openclipart.org/cgi-bin/navigate, is an archive of user contributed clip art that can be freely used.
Images of American Political History, http://teachpol.tcnj.edu/amer_pol_hist/ collects 500 images, obtained from government holdings and from published works with expired copyrights, to support teaching.
US Government Graphics and Pictures, www.first-gov.gov/Topics/Graphics.shtml
More information: http://mciu.org/~spjvweb/cfimages.html
These sites were derived from an article in the Philadelphia Inquirer, October 30, 2005