Ask the guy typing answers on an iTouch.

Yup. iPod Touch can be jailbroken, which allows you to run any software you want on your phone, even if Apple refuses to list it on the app store. In addition, an iPhone can be unlocked, which allows any SIM card to be used with the phone. Unlock does not apply to iPod Touch for obvious reasons.

Jailbreaking will void your iPod Touch warranty as well.

I’m typing this post from my Zune HD. I refuse to be Apple’s slave.