This is basically the short version as there is a lot going on the in Iphone Community. First of all, the Jailbreak for the 3GS is apparently done and ready. This, however, will not be released until FW 3.0.1. If it was released any sooner, Apple would patch the security hole and no other new Iphone 3GS owner would be able to jailbreak. The Dev Team is going to wait till 3.0.1 so more people will have the option of a Jailbreak. If you own a 3GS and want to be able to Jailbreak you MUST follow these instructions.
Obtaining your ECID (or use tools below):
1. Download USBView from here.
2. Put your iphone into DFU mode (hold the power and home for 10s then home for 30s)
3. Start USBView and go to Options -> Config Descritors
4. Go to File -> Refresh
5. Find your IPhone ECID (It’s the 16 digit hex number after “ECID:”)
6. Go to purplera1n, type it, and hit enter.
7. Save the generated file
** To recover your IPhone from DFU just hold Power+Home for a minute until the phone starts again **
Basically the ECID is needed for the Jailbreak.
From the Dev Team:
“The nature of the 3GS hardware allows Apple to stop IPSWs from being usable unless you’ve already gotten the signed chunks they send to you based on your ECID (a unique chip ID). You cannot get these signed chunks without knowing your ECID, and you don’t know your ECID until you’ve bought your 3GS.
The jailbreak requires at least one signed iBoot-family img3 for your device. And that iBoot needs to have an exploitable bug. It’s an all-or-nothing deal…you either have your signed exploitable iBoot ready to use, for now and forever — always jailbreakable — or you have nothing.”
– Hope this helps you new 3GS users (I know I will be buying mine sooner than later)
*UPDATE* This link you might also find useful
*UPDATE 2* Stay away from 3.1 and use this to make a future unlock possible.