For all you Apple users with jailbroken devices, itching to try out the iOS 5.1 firmware update, here is a good news for you. The iPhone Dev-Team has announced that Redsn0w 0.9.10b6 can be used to maintain tethered jailbreak while upgrading to iOS 5.1.
But there is a catch. Only users of the original iPad, iPhone 4, iPhone 3GS, and iPod touch can upgrade and jailbreak iOS 5.1 as they are non-A5 based devices. Users with A5 based devices like iPad 2, iPhone 4S and the new iPad are required to wait till the developers find a proper exploit.
As you might already know, this will be a tethered jailbreak which means you are required to connect to a computer and run the redsn0w software every time you reboot the device. There are many more caveats as explained by iPhone Dev Team here. So be sure to go through the post in detail before you take a plunge.
My personal advice would be to stay away from iOS 5.1 upgrade as it brings hardly any new features or improvements on to the table. If you still insist to be adventurous, check out the download links for redsn0w below:
If you need a step-by-step guide, check out this post by redmondpie.