Redsn0w 0.9.11b4 has just been released, completing tethered jailbreak support for iOS 5.1.1 on all devices except for the iPhone 4S, iPad 2, and new iPad. The release also includes proper “stitching” and “custom” creation of NO_BB IPSWs.
For users attempting to downgrade their devices with iOS 5.1.1, the new version stops the previous failed restore messages. Redsn0w 0.9.11b4 also does not interfere with nearby devices with the option of Wi-Fi syncing enabled.
For all iPhone and iPhone 3GS users who want to maintain their baseband, the newest Redsn0w edition can create NO_BB_* custom IPSWs for iOS version 5.1.1.
By using RedSn0w’s “Custom IPSW,” a user can also create a NO_BB_* version of the latest iOS software, allowing the ability to bring back the custom IPSW as an alternative to Apple’s stock version. Restoring your iPhone with an stock Apple IPSW will lock your handset.
As a word of caution, Redsn0w is also a tethered jailbreak solution that requires a computer connection each time you restart your iOS device.
(Via Jailbreak Untethered)