Utilizing partnerships & information to advance invasive species, forestry & agricultural education the Center for Invasive Species and Ecosystem Health has over 120,000 images on over 14,000 subjects with contributions from more than 1600 photographers from all over the world in the Bugwood Image Database System archive. These images are free to download and use for non-profit educational purposes. The only requirement is that the image should be cited properly.
You do not have to be a professional photographer to contribute to Bugwood Images and you retain complete ownership of images you submit. Anyone interested in contributing photographs to Bugwood Images can get more information at: http://wiki.bugwood.org/BugwoodIDS:FAQ.
To see the image archive go to: http://www.bugwood.org/ImageArchives.html.