Creative Commons - Make sure to uncheck both boxes ("use for commercial purposes" and "modify, adapt, or build upon"). You can use Creative Commons to search for copyright-free images, videos, and music from sources like Google Images, Flickr, and Open Clipart Library.
EduPic - Photographs and drawings that are free for you to use
Photo Pin - Copyright-free photos for your artistic use
Pics4Learning - Pics4Learning is a copyright-friendly image library for teachers and students. The Pics4Learning collection consists of thousands of images that have been donated by students, teachers, and amateur photographers. Unlike many Internet sites, permission has been granted for teachers and students to use all of the images donated to the Pics4Learning collection.
The World Images Kiosk - Offers more than 75,000 images for teachers and students to use in their academic projects.