InstaDerby is your daily window into the world where you can share, discover recognize and connect with other Instagramers, anywhere. And try to take better pics than them.
More on them from the horse’s mouth: http://www.instaderby.com/
They even got a write-up on Mashabe 🙂
As you can see, I am not too popular on this thing yet, but I like the idea of photos with a theme!