Purplesn0w has been launched which provides a soft-unlock for your iPhone 3G S. It was developed by George Holtz who developed the jailbreak tool for the 3G S iPhone.
The reason purplesn0w has been created was due to him being unsatisfied with the Dev Teams redsn0w 3G S tool.
First off, what is purplesn0w? It's a soft unlock for your 3GS that I'd actually use day to day. It's not a daemon that takes any resources, and it doesn't add a task to your baseband. It's very close to a true unlock. All it does is patch three files, CommCenter, lockdownd, and your wildcard activation plist (which you need, activate w at&t sim first, no hacktivation support yet). That's it, no other files are installed.
Details of how to get purplesn0w working can be found here.
Via: TechChee