Stock Exchange (highly recommended)
Morguefile (highly recommended)
Image After
Free Photos Bank
OpenPhoto
BigFoto
USDA
NASA
NOAA
NPS
Earth from Space
FWS1
FWS2
Picture Station
Geek Philosopher
Free Images
Pixel Perfect Digital
FreeFoto
Image Base
Cepolina
Amazing Textures
Texture Warehouse
PDPhoto
Image Blowout
Piotrpix
Mandragora
Fotogenica
Mayang
Free Photo Station
Cromavista
Afflict
Creativity 103
The Photo Repository
Aarin Free Photo
Stockvault
Designpacks
Unprofound
Four Bees
Insect Images
Free media Goo
Burning Well
A digital Dreamer
Freestockphotos.com
Freewebpics
Lightmatter
Majestic Imagery
Triparalbum
Demny Onink
Twice Pix
AboutPixel
Woophy
Pixelquelle
Litetek
PIX
tOfz
Fontplay
Orangetrash
ArtFavor
ImageTemple
LogoDesignweb
Fotodatebank
Bajstock
Pixelbag
NWYH Stock Images (Thanks Richard)
PhotoCase (Thanks Ingo)
NPS Digital Image Index (Thanks Jersu)
Gimp-Savy (Thanks Jared)
DeviantArt
Finally don’t forget to visit
Yotophoto Free photos search engine
and Flickr (be sure to check the licence before using any of the photos).
If you know of any others stock photo resources reave a comment and I will add them to the list.