Fotopedia is a service that combines photos with articles found on wikipedia.  The fotopedia community member upload their own photos and match them to various wikipedia artilces.  If you want to contribute your own photos you need to become a member, but anyone can search for FREE (my favorite word). The quality of the images is outstanding.  This would be a great place to find some visually appealing images to spruce up your classroom instruction.  If you publish anything using the images, be sure to check out the licensing so the copyright police do not come and take you away.