The iPhone Dev-Team has updated PwnageTool with support for the iOS 5.0.1 untethered jailbreak. PwnageTool lets you easily create a custom ipsw for upgrading to iOS 5.0.1.
PwnageTool 5.0.1 supports iPhone 3GS,
You can download the new version of PwnageTool 5.0.1 from
UPDATE: Here are our step-by-step tutorials that will guide you through all the process of untethered jailbreaking iOS 5.0.1 with PwangeTool 5.0.1: