The official PwnageTool 4.1.3 Unlock Edition is now available for download. This version of PwnageTool comes with ability to jailbreak and unlock iPhone 3GS & 3G 4.2.1 iOS. You can unlock baseband 05.14.02 and 05.15.04 using the updated ultrasn0w 1.2. PwnageTool 4.1.3 is for Mac only, Windows users should wait for an update to redsn0w 0.9.6 beta 4 that will let you unlock iOS 4.2.1 on iPhone 3GS & 3G. Here is the download link:
Download PwnageTool 4.1.3 [PwnageTool_4.1.3_Unlock_Edition.dmg.5994102.TPB.torrent]
A how-to guide will be posted soon that will help you jailbreak and unlock 4.2.1 iOS for iPhone 3GS and 3G, stay tuned!