Array.prototype.shuffle; ref: http://la.ma.la/blog/diary_200608300350.htm

Array.prototype.shuffle.js

Array.prototype.shuffle = function() {
  var i = this.length;
  while(i){
    var j = Math.floor(Math.random()*i);
    var t = this[--i];
    this[i] = this[j];
    this[j] = t;
  }
  return this;
}