Many listeners of classical music like to organize and browse their music library by composer, rather than artist or performer. Unfortunately, iTunes only allows browsing by artist, album and genre. Here is my workaround: swap the contents of the Genre and Composer fields, and enable 'Show genre when browsing' in iTunes' preferences.
Run this AppleScript on all tracks of your iTunes library, and from then on, run it systematically on all newly added music. (It is assumed that you do not use the BPM (beats per minute) field. Note that this script was inspired by one found at Doug's AppleScripts for iTunes.
[robg adds: I haven't tested this one...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060728075406907