Bugwood Images provides an easily accessible archive of high quality images for use in educational applications. It is made up of five major website interfaces, ForestryImages, IPMImages, InsectImages, WeedImages, and Invasive.org. Images included in the Bugwood Network Image Archives are made available under a Creative Commons license. Individual photographers retain all rights to images included in the archive under variuos Creative Commons licenses. Requesting and using images from the Bugwood Network is described here, Image Usage.
The USDA NRCS (Natural Resources Conservation Service) Photo Gallery contains natural resource and conservation related photos from across the USA. Photos in the Gallery are available free of charge in two common image formats: TIFF or JPEG. Attribution (Credit) to the photographer/site is required.