Syncing Jailbreaked Ipod Touch
You can unjailbreak an iPod or any other iDevice by restoring the device from a previously unjailbroken backup or you can download the latest update from Apple for your device and install that. IF there is one. 

Apple doesn't want people jailbreaking so all you have to do is update the IOS or restore to an old non-jailbroken copy and it will 'unjailbreak' it.