How can I randomly show a set of elements using jQuery?

Object.extend(Array.prototype, {
  shuffle : function() {
    this.sort( function() { return 0.5 - Math.random(); } );
    return this;
  }
});

var intervalMilliseconds = X; // set to your value for X
var divFoos = $("div.foo").get();
var intervalId = setInterval(function() {
   $(divFoos.splice(Math.floor(Math.random() * divFoos.length), 1)).show();
   if(divFoos.length == 0) clearInterval(intervalId);
}, intervalMilliseconds);

(function () {
    var int, els;
    int = 100; // interval, in milliseconds
    els = $('div.foo');
    setInterval(function () {
        var idx;
        idx = Math.floor(els.length * Math.random());
        $(els[idx]).show();
        setTimeout(function () {
            $(els[idx]).hide();
        }, int);
    }, int);
})();