While playing a song on the iPod, holding the > keys will scan backward and forward; this is old hat. But if you click the select button (center), the progress bar turns into a little diamond indicator and the scroll wheel can be used to scan. Pretty cool.
[Editor's note: Yes, I realize an iPod hint is not an OS X hint ... but I also know a lot of you have them, so I thought this might be of interest. I'd test this hint myself, but I'm still pod-less...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030131055058178