Uninstalling MySQL on Mac OS X involves manually removing following directories and files from your drive.
Assuming your MySQL is installed in /usr/local, perform the following steps:

1. cd /usr/local
2. sudo rm mysql removes the symbolic link to the actual mysql installation. You may be prompted for your administrator’s password at this point.
3. sudo rm -rf mysql-5.1.47-osx10.6-x86/ removes the actual mysql installation. You may have a different version of mysql installed on your system.
4. sudo rm -rf /Library/StartupItems/MySQLCOM removes the MySQL startup option.
5. rm -rf ~/Library/PreferencePanes/My* removes preference panes.
6. sudo rm -rf /Library/Receipts/mysql*
7. sudo rm -rf /Library/Receipts/MySQL*

I was hoping for a much simpler process for cleanly uninstalling MySQL from my system.
Thanks to Rob Allen for this tip: Rob Allen’s DevNotes