This is works for all of them except for the Ipod Touch 2G.
First off you will need Quickpwn
Windows Version:
http://quickpwn2-2-1.googlecode.com/fil ... -225-2.zip
Mac Version:
http://quickpwn2-2-1.googlecode.com/fil ... _2.2.5.dmg
This Quickpwn works for all of the versions between 2.0 - 2.2.1.
Next, I recommend using the computer you usually use to sync your phone with because it will have the original ipsw of your Ipod/Iphone. (ipsw is Ipod software)
Open Itunes and let it recognize your Ipod/Iphone. Quickpwn will automatically close Itunes once it gets into hacking.
Run Quickpwn and cross your fingers it will find your ipsw and you will have it easy. If it doesn't find you ipsw you can search google for your current version and download it onto your desktop.
(the ipsw is like 500mb so it will take a while)
Before skipping ahead in Quickpwn I think the 3rd or 4th step is the hard part.
It will be a set of instructions that I will tell you from now, because if you mess these up you will have to force restore your Ipod/Iphone.
1. It will first be hold home button.
2. Now DO NOT LET GO OF HOME hold home and power together.
3. Let go of power and keep holding home until it stops the timer.
I am sorry but I do not remember the time but it was something like 5 seconds then 10 then 30.
Now leave your phone for a couple minutes and when it says your Ipod/Iphone seems to been Jailbroken correctly close quickpwn and unplug your Ipod/Iphone.
If the Ipod/Iphone does not start up then it was messed up and must be force restored.
To force restore:
1. Turn off the iPhone (you can hold down the Sleep button, or use Sleep + Home, and release as soon as the screen shuts off).
2. Hold down the Home button while connecting to your computer with iTunes already open and ready for a connection.
3. iTunes will prompt you to perform a software restore.
4. Your iPhone will obviously be wiped new and be reset as a result and you wil have a working iPhone again.
Then you can try again. And not mess it up.
Good Luck!
EDIT: THE NEW MAC LAPTOPS CAN NOT HACK IPODS OR FORCE RESTORE IT!!!