If you think FaceTime feature will only be available for iPhone 4 and iPod Touch 4G users, you got it wrong.
Folks at iPhoneIslam posted a video in YouTube showing FaceTime enabled on jailbroken iPhone 3GS. Though the 3GS has no front-facing camera, the team is working to activate the rear camera for video calling. Enabling FaceTime on iPhone 3GS is achieved using an app called FaceIt available on Cydia.
FaceIt will be released soon, so just stay tuned for updates! [via]