Hot air balloons that appear, roam through your mind, and then disappear.
This dream consists of three images: one of the sky/clouds, and then one for each of the balloons. The presentation adjusts the opacity of the balloon images, as well as their size and position. I spent a good deal of time tweaking the easing between the various stages of animation to get (what I hope is) a realistic effect to their movement. jQuery to CSS3 transition support is provied by the excellent jQuery Transit plugin.
All modern browsers. The version for Internet Explorer 9 is dumbed down slightly. Other browsers are served static, non-moving images.