I just installed mysql on a mac running 10.6. The mysql version is 5.1.56. I need to have mysql run on port 3307. This article says we can change the port by modifying this file
On OSX you can create /etc/my.cnf if it does not exist. You can base it on samples found in /usr/local/mysql/support-files. Don't forget to restart MySQL for your my.cnf to take effect.