How do I hack my iPod to get free games if I have a Mac?
If it's an iPod Touch you will have to jailbreak it. There are various ways and tools to do this. Which one to choose depends on your device generation and the iOS Software you are currently using.
If you have an iPod which isn't based on iOS your only chance is to install a linux designed for that purpose (http://en.wikipedia.org/wiki/IPodLinux)
Consider your self warned: Both will void your devices warranty.