I actually saw a confrontation between some juggalos and some goth kids at a mall a few months back. it was like watching rival gangs encounter each other but around 50x more lame. A pair of juggalos were walking around with their insane clown posse makeup on and some group of goth kids fresh out of hot topic head over to poke fun at them. If only a fight would have started, alas they just exchanged words and went on their seperate ways... how lame.
i'd classify it under furry, although a few might just be run of the mill anime geeks and may not necessarily be furries.
As for what a juggalo is... http://images.google.com/images?svnum=10&hl=en&lr=&q=juggalo&btnG=Search basically a white trash teen with an intense burning desire to put on angry clown make up and listen to songs about sinister evil clowns by the Insane Clown Posse or one of the other 3 dozen sub-bands.