carousel.js

$(function() {
  var $slider = $('.slider'),
      $first  = $slider.find('.picture:first'),
      skipNextFade = false,
      fadeTo = function($to) {
        if (!$to.is(':visible')) {
          $slider.find('.picture:visible').fadeOut(1500);
          $to.fadeIn(1500);
        }
  };

  $('.slider-controls a').click(function(ev) {
    ev.preventDefault();
    fadeTo($slider.find('.' + $(ev.target).data('class')));
    skipNextFade = true;
  });

  setInterval(function() {
    var $maybeNext = $slider.find('.picture:visible').next('.picture'),
        $next      = $maybeNext.length === 0 ? $first : $maybeNext;
    !skipNextFade && fadeTo($next);
    skipNextFade = false;
  }, 10000);
});