The recently released Redsn0w 0.9.6b3 can jailbreak all iOS based devices including the new A4 devices like iPhone 4, iPad and iPod touch 4G. Since Cydia included in this version of Redsn0w is not compatible with iOS 4.2.1, you can use the following steps to install a patched version of Cydia.
Since Cydia is broken on iOS 4.2.x, the new Redsn0w 0.9.6b3 released today supports iOS 4.2.1 so that developers can make their jailbreak-apps compatible before Apple releases the final firmware to public. Using this version of Redsn0w, you can now install jailbreak-apps without using Cydia.
