Open Clip Art Library has a large collection of more than 40,000 images free for anyone to use. There are tons of images here useful to teachers and students. Some of the clipart is in collection packages on themes such as spring, sports, Thanksgiving, etc. Or you can search for individual images. There is lots of science clipart for astronomy, plants, chemistry, and physics. There are images of kids and animals and clip art for math concepts, historic figures, cultures and countries, to name a few. You have the ability to use an online editor for many of the images.