For those folks who have upgraded to firmware 3.1.3 and tried to jailbreak their iPhones or iPod touch with redsn0w 0.9.4 but could not do so for any reason or are stuck and want to restore their older firmware 3.1.2, here are the high-speed direct download links. Let us know if you are facing any problem after jailbreaking your iPhone 2G and 3G or iPod touch 2G and 3G (non MC older models).
Download iOS/iPhone firmware for iPhone (2G, 3G, 3Gs and 4), iPod Touch (2G and 3G) and iPad
Important
Now you can do untethered Jailbreak of your iPhone 3G/3Gs running latest firmware 3.1.3 with "Spirit".
Step by Step iPhone and iPod Touch (All models) Firmware 3.1.3 Jailbreak Guide Using Spirit
If you want to restore your iPod touch back to firmware 3.1.2 then here are the direct high speed download links:
Download firmware 3.1.2 for iPod Touch 3G
Follow this guide on how to downgrade your iPod touch 3.1.3 to the newly downloaded firmware 3.1.2 IPSW.
Update:
Apple has stopped signing the firmware 3.1.2. See the link to know what it implies for your iPhone.