Animals/wildlife

 

http://gimp-savvy.com/PHOTO-ARCHIVE/

http://pdphoto.org

http://pics4learning.com/

http://en.wikipedia.org/wiki/Wikipedia:Public_domain_image_resources

http://www.publicdomainpictures.net/

Countries

http://www.graphicmaps.com/clipart.htm

http://pdphoto.org

http://pics4learning.com/

http://en.wikipedia.org/wiki/Wikipedia:Public_domain_image_resources

Maps/Flags

http://www.graphicmaps.com/clipart.htm

Nature/Environment

http://gimp-savvy.com/PHOTO-ARCHIVE/

http://www.freeimages.co.uk/

http://www.freephoto1.com/

http://www.photolib.noaa.gov/

http://pics4learning.com/

http://www.publicdomainpictures.net/

Space

http://gimp-savvy.com/PHOTO-ARCHIVE/

http://www.freeimages.co.uk/

http://grin.hq.nasa.gov/

Weather/Disasters

http://gimp-savvy.com/PHOTO-ARCHIVE/

http://www.photolib.noaa.gov/

http://pics4learning.com/

Plants

http://pics4learning.com/

http://bio.ltsn.ac.uk/imagebank/

http://www.freephoto1.com/

http://gimp-savvy.com/PHOTO-ARCHIVE/

http://www.publicdomainpictures.net/

Food

http://www.freeimages.co.uk/

http://www.freephoto1.com/

http://www.publicdomainpictures.net

Ancient History 

 

http://www.metmuseum.org/home.asp

http://pics4learning.com/

Transportation/

Technology

http://pics4learning.com/

http://pdphoto.org

http://www.freephoto1.com/

http://www.freeimages.co.uk/

War/Military

http://www.gwpda.org/photos/greatwar.htm

http://www.fdrlibrary.marist.edu/archives/collections/photographs.html

http://www.dotgovwatch.com/?/archives/8-The-Best-Copyright-Free-Photo-Libraries.html

Sports

http://www.clker.com/

http://www.sxc.hu/