You may or may not be aware of the iTunes visualizer. It's a nifty little tool that gives you something fun to look at on your screen while you are playing music in iTunes. To turn the visualizer on, just click on the button in the lower right-hand corner of iTunes (as shown below):

After you turn the visualizer on, it will look like this:

I don't use it very often, but when I do, I like to control it to do what I want it to do. There are a few keys that you can use to do this. Give these a try:

C: Shows the current effect

Q & W: Cycles through the foreground patterns

A & S: Cycles through the background patterns

Z & X: Cycles through the colors

Shift+0-9: Saves current effect combinations

R: Turns on random effects