Black sun animation in iTunes. Does anyone know what it is?
That is the Visualizer.  You can press Command + T (Ctrl + T on Windows) to start it.  Or it is available form the View Menu.

View --&gt; Show Visualizer


Also in the View Menu you can change some of the settings for the way the Visualizer looks.

View --&gt; Visualizer --&gt; &lt;More Options Here&gt;