For Windows:

Step 1: Download redsn0w , 3.0 Firmware and iTunes 8.2

Step 2: Connect your iPod Touch to computer

Step 4: Start iTunes 8.2 & Select iPod Touch from devices list

Step 5: Hold Shift and click Restore

Step 6: Locate iPod Touch ipsw files downloaded in step 1

Step 7: Do not disconnect till iTunes has completed updating iPod Touch

Step 8: Run Redsnow and follow intructions

Step 9: Enjoy your new Jailbroken 3.0 iPod Touch!