iPhone Dev Team member wizdaz has announced the port on his Twitter account few hours ago:
ported new LimeRa1n bootrom exploit into PwnageTool
So, PwnageTool now may work on iPhone 4, iPhone 3GS (both old and new bootroms) and iPhone 3G. You will be able to create custom firmware using the new version of PwnageTool and be able to unlock your iPhone carrier using Ultrasn0w via Cydia. We will keep you updated, stay tuned!