More often than not, the success of a website will hinge on its apparent simplicity, no matter how complex the engine that drives it.
Case in point, the frankly incredible Music-Map, a website which will take a band or musical artist and return a cloud of associated and similar acts. From there, you can either start over with a new band, or click on one of the orbiting options in order to follow the links between, say, Bob Marley and Mindless Self Indulgence.
Created as part of the Gnod artificial intelligence project by Marek Gibney, the system has already been adapted to map films, books and even people.