Dev Team just released redsn0w 0.9.10 beta 6, a new version of the free jailbreak tool that helps us to perform a tethered jailbreak on iPhone 4 running iOS 5.1. Unfortunately iPhone 4s is not included in the list of Apple devices compatible with this jailbreak tool but the rest devices that can run iOS 5.1 can be jailbroken using the latest version of redsn0w.