$(document).ready(function() {

  var words = ['a', 'b', 'c', 'd'];

  var getRandom = function() {

    var idx = Math.floor(Math.random() * words.length);

    // grabs word and removes it from the array

    return words.splice(idx, 1)[0];

  };

  var appendIfMore = function() {

    var word = getRandom();

    if (!word) return; // all done

    $('<div class="conversation"/>')

      .text(word)

      .appendTo('#container');

    var delay = Math.round(Math.random() * (3000 - 500)) + 500;

    setTimeout(appendIfMore, delay);

  };

​

  // start appending stuff

  appendIfMore();

});