To start off on the 3.0 firmware jailbreak you first have to have Itunes 8.2 and you have to download redsn0w for windows or for the Mac. 

Go to this site: http://www.iphoneworld.ca/news/2009/06/20/download-redsn0w-mac-windows-iphone-2g-3g-itouch-unlock-hack-for-firmware-v30/  

When you get thier scroll down until you see " Direct Downloads" click on ethier Windows or Mac. You should Download Winrar from google before. Now when your download is done open it. It will ask you to select your current firmware. Now you have to download the 3.0 firmware for your device.

Ipod touch 1G: http://www.megaupload.com/?d=VFDD6QP1

Ipod touch 2G: http://www.megaupload.com/?d=XVS5J8D8

Iphone 3G: http://depositfiles.com/en/files/pnj6xzh5n                                                            (click on free downloading when you get their, then you will have to wait about 60 seconds or a little more)

Now back to redsn0w. Click on browse and select the firmware that you saved ( save it in a easy to find folder like my documents). When you see that it says IPSW successfully identified hit next. When it says connecting to server put your ipod/iphone DFU. To put your ipod into DFU mode Hold the power button and home button for 10 seconds and then let go of the power button but kept holding the home button (make sure your ipod/iphone is off) for a few more seconds. now click next and select the option (if not all ready) install cydia. Click next.

Now before you click next make sure your ipod/iphone is off and pluged in. Now before you click make sure your ready because this all happens really fast. Click next and click the power button until is swiches to the next step (about three seconds) now quickly hold the power and home button for 10 seconds then quickly let go of the power button but keep holding the home button for 30 seconds. Note: the time you still have left is under the text of each step.Now keep holding home until it goes onto the next step and your screen turns white, when it turns white you can let go. Now wait while its processing and your ipod/iphone screen will eventually say downloading jailbreak data, keep waiting until the process is done then hit finish. Your ipod/iphone will still download the jailbreak data. After that your ipod/iphone should reboot. It will have a black screen just wait a few seconds and it should come up with your side to unlock screen. After that you then should have cydia and congrates you just jailbroke your ipod/phone with 3.0 firmware!

I'm not responsible for your ipod/iphone if this does not work, it worked for me and my friends. If it doesn't im sorry but it should work. If not try to restore it in itunes.