NameThatDisease.com - The disease test
The idea is that you have to identify 15 diseases based on clues; it gets easier as you go along, once you've eliminated some possibilities. (I identified each disease correctly, but I needed extra clues on some of them.) Mind you, I did see the same photo for two different diseases so I'm not quite sure about the accuracy there. The only improvement I'd make to their scale of results is to add Greg House.
(Link via Trauma Queen.)