The Yahoo! owned photo site Flickr is unique compared to some other photo hosting sites on the web like Snapfish (which I use and is owned by HP) or Shutterfly in that Flickr was designed to have hosted photos easily viewable by the public. The result of this is a huge network of people and images with recommendations being made, comments posted and images linked to.
Out of all this interaction, Flickr has developed an algorithm that results in their "most interesting photos"... which is constantly refreshed and features what Flickr feels are the most interesting from the last seven days.
The URL is here and images can either be viewed by this opening page, by clicking on a given picture or in slideshow form.
Just for giggles, I've posted below the first image that appears right now (which will be of course different in a day/week/month)...

Really cool stuff.