This is a small hint, but it comes in handy if you edit iTunes files outside of iTunes. iTunes tracks files by inode (as does the Finder), so renaming a file and putting another in its place won't work.
This Perl script overwrites a file in place, preserving the inode. You can edit a copy of the file using any tool you wish, and then use this script to replace the original. iTunes will then use the new file. It won't notice changed tags immediately, but if you try to edit any of the track information, it will update with the correct information before letting you edit.
[robg adds: I haven't tested this one. Make sure you make the script executable with chmod 755 script_name before you try to use it.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20041212201714278