Could this be the Best Place to Find Free Clipart and Other Images for eLearning?
If you are looking for copyright free icons, diagrams and a wide range of clip art, Clickr and Open Clipart are good places to start. I used Open clipart (http://openclipart.org/) recently to find images for some anatomy and physiology resources. For example, I found an excellent skeleton that I could download in .png (bitmap, for instant use) or .svg (vector, for editing) formats. I was also able to edit them online with imagebot (http://www.flamingtext.com/imagebot/) which is a reasonable bitmap based editor.
Clickr Clip Art (http://www.clker.com) is similar and uses a vector editor (Open SVG) which allows you full control over vector points (you have to double click objects to go into vector mode). Also, if you upload a photo of more than 1 megapixel it will automatically vectorise it, which gives photos an illustrated appearance.
Open SVG is a very useful tool for those who don’t need Illustrator or Inkscape, but sometimes need to do some vector editing. Here is a short Youtube demo.
If you need high quality images for education or even commercial use www.pixabay.com has some really beautiful, professional quality photos and illustrations on all topics, and they are all completely free for any use. www.morguefile.com is another site where you can find public domain images on many topics.