If you have upgraded your iPod Touch software to version 1.1.2 (as I did) then you currently need to "downgrade: to 1.1.1 before you do a "jailbreak". The best instructions I have found so far are here.

I am currently doing this to my iPod - and will add comments later.

Update

I have now (after applying the necessary files) upgraded to 1.1.2 and installed the iPhone software such as Google Maps and Mobile Email, and it all works - although Email seems to be a bit more touchy when it comes to setting up IMAP emails accounts than it used to be.

But everything works - so I'm a happy camper.

Now that version 2.1 of the iPhone/iPod touch has been released for the iPod Touch (so I expect it to be available for the iPhone very soon (?)) - at the very least there is a list of what has changed :

I have to admit that I have used the iJailBreak utility to update my iPod Touch, and add the rest of the iPhone software to this now even more attractive device. So now I have email and Google maps available!

I've updated my (non-jailbroken) iPhone on the second try. My iPod Touch will follow later when I'm sure it can stay jailbroken.

On Tuesday, Apple released version 1.1.4 of its firmware for the iPhone and iPod touch handsets. While little is known as to the changes represented by the update, users can download and install the 162.1 megabyte file by docking...

[From Apple Releases iPhone/iPod Touch Firmware Version 1.1.4]

If you have done the "JailBreak" and installed applications on your iPod Touch then you could do worse than spending a few moments to change the root password - as this is known on the Internet.

So go to the "Settings" panel, and find your iPods IP address (in my case 192.168.0.138) - ssh into it like this :

ssh root@192.168.0.138

when asked for the password :

password: alpine

and then

passwd

to change the password to something else.

Please be aware that first time you log into your iPod Touch with ssh it will need to generate a set of keys, which will take a little bit of time.