Have you ever done a job and needed an existing logo for a well known brand but for love or money your client just can’t get hold of one. They send you a rough gif and say “will that do?” No I am not saying these sites are ideal, you should always get the proper logo if possible but it sure beats trying to retrace a logo or use a patchy gif –

http://logotypes.designer.am/srch/search.php

http://www.brandsoftheworld.com