PIC Findr - Searches Multiple Image Sites & allows you to filter by license type so that you only look for images that are not copyrighted. http://www.picfindr.com/app/?search=
WP Clipart http://www.wpclipart.com/
Open Photo http://openphoto.net/search/index.html
Stock Exchange Photo http://www.sxc.hu/
FreeFoto http://www.freefoto.com
Pics 4 Learning http://www.pics4learning.com
Flickr - Creative Commons http://www.flickr.com/creativecommons
Microsoft Online Clipart http://office.microsoft.com/en-us/clipart/default.aspx