At Kittenwar.com they show you two pictures of kittens with a big clear "vs." between the two pictures. You vote for wich one you think is the cutest. The "battles" are randomly selected and sometimes you have to say that an not-so-cute kitten is the winner even though you'd rather just pass that battle.
This idea is really clever because with the random element it does a "randomly permutative" comparison between as many pictures as possible. This is much better than sites Hot or not where you select on a Lickert scale how much you like each picture.
But for this to work, it must be dead clear what the criteria is that you're comparing with. If the criteria on kittenwar.com was "finest fur" the results would be very different.
The voting system on kittenwar.com really excites me because not only is it very very fair, it also enables the voting arranger to pin point exactly the question that people should consider. For example, I could have battles like "Most impressive screenshot" or "Most inspiring screenshot" of these pictures for example.
If you visit Kittenwar.com now make sure you don't miss the winningest kittens because it will really melt your inner child like chocolate. I guess it can be quite an embarrasment too. I wouldn't want to be the owner of this cat for example.
My site is somewhat more artificial, but I hope you will like it... Enter and vote!
YES IT IS GREAT BUT IM SORRY I JUST LOVE KITTEN WAR
I THINK KITTEN WAR IS ABSOLUTELY FABULOUS AND IT IS RALLY SWEET BUT SOMETIMES IT CAN BE REALLY HARD TO CHOSE AND I CANT HELP BUT HUG MY SELF AND STROKE THE SCREEN WHEN I SEE A REALLY CUTE CAT
You should really try http://www.likebetter.com/channels - it's like kittenwar as you say, but you can make your own channels (like for screenshots), and there's all sorts of stuff in there.
It allows you to leverage the pairwise-style voting seen on kittenwar.
"not only is it very very fair"
You must be joking. It's the pictures, not the kitten.