Here are the instructions on how to jailbreak your iPod touch 3G on the 4.3.2 firmware using RedSn0w for Mac.
First you need to open a Pwnage folder on your desktop
Download RedSn0w and place it in the Pwnage folder. Again download the latest 4.3.2 firmware from below and keep it in the same folder.
4.3.2 (3G): iPod3,1_4.3.2_8H7_Restore.ipsw
Download Redsn0w 0.9.6rc14 for Mac
Select your iPod touch from the list of devices on the left. Hold down option and click the Restore button.
Now you can connect your iPod to the computer and launch iTunes.
Select your iPod from the list of devices on the left. Now hold down Option and click the Restore button.
Navigate to the Pwnage folder on your desktop and select the 4.3.2 firmware ipsw. Select the choose button to continue.
Once iTunes has finished updating your iPod to the desired firmware open the Pwnage folder on your desktop and launch the redsn0w application from the redsn0w folder.
Make sure Cydia is selected and click the Next button to continue.
[ image courtesy ianmarmour ]