DeskTunes is a very simple, very elegant way to see what's playing in iTunes right now. It stays stuck to the bottom left corner of the Desktop, no matter what you do. It even stays put if you try and hide all of your windows with Exposé. You can also rate the currently playing song by clicking the star bar. Simple. Elegant. Tiny. Out of the way. Beautiful.
Mac OS X 10.4 or later, iTunes 6 or later
*Previously available here