Not sure if its iTunes3 or 10.2, but in iTunes if you are in browse mode with all four panes (genre - artist - album - library) and you have a scrollwheel mouse, you can hover over the pane you want and just scroll away to your hearts content! AWESOME!
[Editor's note: This also works when just two panes are onscreen. I could not find a way to scroll with the keyboard, however, so it looks like a scrollwheel mouse is required.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020901085723295