The jailbreaking saga continues. As soon as Apple released OS 3.1.3 for the iPhone, the legendary Dev Team got to work. However this time don't throw caution to wind and jailbreak your device at your own discretion. As of now only the iPhone 2G, iPhone 3G, and the iPod Touch 1G can be jailbroken, which means 3GS owners have to play the waiting game which putting it eloquently, just blows! So if you don't own the iPhone 3GS and itching to jailbreak your updated device just follow the instructions below.
The first step involves you downloading the latest 3.1.3 firmware from iTunes and the RedSn0w 0.9 jailbreak like before. When you download RedSn0w 0.9 , then opt for 3.1.2 as the firmware.
Once you launch RedSn0w, it will check if you chose the correct firmware and then will patch the file.
If you have never jailbroken your device and want detailed instructions then you can read our tutorial here.
You can also read observations made by Dev-Team on their blog here.
Accessories & Apps: Beta Testers Wanted
iOS Firmware/IPSW Download Guide
Legacy iTunes Download Archive
App Store Top Charts
iPhone and Android Resale Value Charts
USA iPhone Carrier Plans Compared
Complete iPhone Jailbreaking Guide 
Complete iPhone Specification Matrix 
HOW/WHERE do I find the corresponding IPSW for my current firmware?
http://www.ismashphone.com/2009/06/iphone-os-downloads-to-rescue-failed-iphone-hacks.html links to IPSW files are here
I’m a little confused. It says don’t do the upgrade to 3.1.3 on a 3GS if you want to keep your unlock. My phone was bought in Hong Kong and is factory unlocked for any SIM card. Indeed it worked with any SIM card before I jailbroke it. Therefore I don’t need to jailbreak in order to unlock it. Does that mean that I can upgrade to 3.1.3 and then jailbreak with redsn0w without any hesitatations?
This didn’t work when I tried it yesterday. I am sure that when I read these instructions then it said this doesn’t work for 3G. You can vouch it works?
You’re all good. It’s just warning against the people with att phones and such, that aren’t already factory unlocked.