Have you already updated your device to the version iOS4 and want to unlock your 3GS? Firstly there was Redsn0w, now PwnageTool is available, which can easily help you. Here is for jailbreaking iPhone 3GS (old bootrom). Warning: this is not an official release and therefore may be some bugs that can destroy your device or delete some important information. So be careful while using it!
Thanks to and the porting work of as well as the authors of , it is now possible to “tether” your iPhone 3G and use its Internet connection on your laptop.
Warning – Tethering your iPhone is against the iPhone data plan terms. AT&T could slap you with huge fees if you overuse this. I recommend only using it during emergencies.
Here is a basic plan (by the way, this should work for old IPhone also):