Download the latest version of You must login or register to view this content. and follow the steps to jailbreak untethered (It works on 5.0 and 5.0.1).
The following user thanked Shebang for this useful post:
It is possible to jailbreak the ipod touch 4G on 5.1?
Yes wirh redsn0w but the jailbreak is tethered and if you turn off your iPod then your apps are crashing and you have to reboot it on your PC that sux.