Warning! Thread Creep...
Re mentions of 'Ring a Ring of Roses' above, I've always been told that it relates to the plague as follows:

Ring a ring of roses (refers to ring-shaped rash on skin)
A pocketful of posies (refers to medieval custom of carrying herbs/flowers to ward off illness and bad smells from sick people!)
A-tishoo! A-tishoo! (sneezing...duh)
We all fall down. (dead)