Fisher-Yates (aka Knuth) Shuffle

Shuffle.js

function shuffle(array) {
  var currentIndex = array.length
    , temporaryValue
    , randomIndex;

  // While there remain elements to shuffle...
  while(0 !== currentIndex) {
    // Pick a remaining element...
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;

    // And swap it with the current element.
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }
  return array;
}

//shorter version
function fisherYates(myArray) {
  var i = myArray.length;
  while(--i) {
     var j = Math.floor(Math.random() * (i + 1));
     var tempi = myArray[i];
     var tempj = myArray[j];
     myArray[i] = tempj;
     myArray[j] = tempi;
   }
}