careful with these. I should say some of these. Some of these sites are fronts simply for gathering images that they then re-sell on photo-cds or other stock photo services. Read their copyrights/privacy/EULAs carefully. The fact that the one you linked to has NO
copyright or poster rights given and just their own "Copyright 2004, AzColt.com" on every page, makes me (the paranoid guy) a little nervous.
Uploading an image to these sites basically gives them the right to market, sell and use your images as they see fit.