In case you are in Middle East, you may know that there's no FaceTime there but some folks got a tweak the MiddleWhat tweak to activate it in unsupported countries. The same folks are now working hard to bring FaceTime on jailbroken iPhone 3GS.
This is thanks to a tweak will be available in Cydia for jailbroken iPhone 3GS running iOS 4.1. The tweak know as “FaceIt-3G” will enable iPhone 4-only FaceTime video calling option on iOS 4.1 for iPhone 3GS users. You can check the video to see it in action.