Brilliant site with copyright free clip art.
http://www.ltscotland.org.uk/earlyyears/resources/illustrations/index.asp

This site has excellent quality clip art for school use.
http://www.dorlingkindersley-uk.co.uk/static/cs/uk/11/clipart/home.html

Another good copyright free web site for clip art.
http://ngfl.northumberland.gov.uk/clipart/default.htm

Very good site for copyright free clip art, with a search option.
http://gallery.e2bn.org/index.php

Lots of copyright free pictures.
http://pics.tech4learning.com/index.php