Here’s one more I found and thought was quite neat. [Link] This site allows you to enter any search term and it will give you a matrix of 36 photos related to that tag. You can click any of the photos to see it enlarged beside the matrix. You can also scroll through the thousands and thousands of other photos with that tag.
The interesting part that gets you to keep exploring here is as you move your mouse away from the photo matrix you are presented with about 40 unique tags related to the original. For example if I start with CAT, I am presented with 1.3 million+ photos. As I move my mouse out other tags that I can now choose from are Baby, Meow, Kitty, Dog, Sleep, Nature, etc. I picked nature and am now sent to 2 Million+ photos to look over with a whole new series of tags to explore.
Truly an interesting way to view photos that have been posted, but also a great demonstration of the power of tags and relationships.