Animate Your Songs: iTunes Visualizer
Visualizer is the iTunes term for an onscreen laser-light show that pulses, beats, and dances in perfect sync to your music. The effect is hypnotic and wild, especially when summoned midway through a sluggish day in the office.
With iTunes 8, there are more visuals than ever to pick from. Choose View→Visualizer to select from iTunes Visualizer (lots of Disco in Space moments) or iTunes Classic Visualizer (trippy psychedelic patterns a go-go). Mac users running OSX10.5, or later, even get three more colorful themes to choose from: Lathe, Jelly, and Stix.
❶ To summon the scenery, choose ViewShow Visualizer. The show begins immediately.

Tip
The keyboard shortcut for turning the Visualizer off and on is Ctrl+T (⌘-T).
❷ If you find the iTunes window too constraining for all this eye candy, you can play it full screen by going to the Preferences box (Ctrl+comma/⌘-comma) and clicking the Advanced tab. Put a check in the box next to "Display visualizer full screen."

True, you won't get a lot of work done, but when it comes to stress relief, visuals are a lot cheaper than a hot tub.