[jr2]

Jailbreak has been available for iOS 5.1.1 A5 powered devices since the 25th.  Google greenpois0n and go to their website.

iOS 5.1.1 support for:

iPad 1, iPad 2, iPad 3 (iPad2,4 is now supported as of Absinthe 2.0.4)

iPhone 3GS, iPhone 4, iPhone 4S

iPod touch 3rd generation, iPod touch 4th generation

How To Use Absinthe 2.0 (if you’re unjailbroken):

1. Make a backup of your device in iTunes by right clicking on your device name under the ‘Devices’ menu and click ‘Back Up’.

2. Once your backup is complete return to your device and go to Settings – General – Reset – Erase all Content and Settings. This will make the jailbreak process much faster.

2¹/₂. At this point, update to 5.1.1 if you haven't already. -jr2

3. Open Absinthe and be sure you are still connected via USB cable to your computer.

4. Click ‘Jailbreak’ and wait…. just be patient and do not disconnect your device.

5. Once jailbroken return to iTunes and restore your backup from earlier. Right click on your device name under the ‘Devices’ menu in the left panel of iTunes and click ‘Restore from Back Up…’ then select the latest backup you created before. (restoring this backup will return all the content previously on your device ie, apps, photos, etc.)

6. Thanks for using Absinthe, enjoy your jailbroken iDevice!

How To Untether 5.1.1 (if you’re already jailbroken):

Just search for and install “Rocky Racoon 5.1.1 Untether” from Cydia.

[Klaustrophobia]

not being an iPhone (or any other smartphone for that matter) user, i've always wondered.  what does jailbreaking even mean?

[jr2]

It means that you can put whatever you want on your phone, without big corporate brother having to give you the ok first.  In other words, if you want an app that Apple or another company doesn't think you should have (perhaps it competes with the built in app, like Safari, or something), now you can download and install it.  Whereas before jailbreaking, you are stuck with whatever Apple / other company has to officially offer, as they locked the phone down.

Another term used for jailbreaking is 'rooting' (although iDevices are usually referred to as 'jailbroken', devices referred to as 'rooted' are usually Android / WinPhone in my experience.

In a nutshell: you take control of the device that you own.  Who would have thought...

[Goober5000]

For those who are curious, jailbreaking is "officially" legal:
http://www.cnet.com/8301-17918_1-20011824-85.html

Which is a good thing, as this is one of those areas where the morally justifiable thing to do isn't obviously legally justifiable.

[Flipside]

Seems to be an untested, and unlikely to be tested, issue in the UK. People should note, however, that doing so will void any warranties you have

[jr2]

I should also point out, that the new Mobile Substrate v. 0.9.3997 and up has a safety feature that should make it impossible to have an issue with a tweak that breaks your device (by disabling all jailbreak features at boot as a 'safe mode'):

http://www.ijailbreak.com/cydia/mobile-substrate-0-9-3997-cydia/

Earlier today we told you that Saurik pushed an update for WinterBoard to make it more stable than it has ever been before, and also bring on support for the iPhone 4S. Now an update to Mobile Substrate has also been released into Cydia bringing Mobile Substrate to version 0.9.3997. In Mobile Substrate v0.9.3997 comes a brand new feature that is best illustrated by Saurik himself:

As of version 0.9.3997, you can now disable Substrate entirely by holding down Volume Up as the device boots.

This feature allows you to bypass horribly broken extensions (ones that prevent the device from starting up at all) that you may have installed so you can open Cydia and uninstall them.

To support devices that do not have a Volume Up button (the first-generation iPod touch), you can alternatively hold down the “Clicker” (not Volume Up) button on your headset or earphones.

(A special thanks goes to @oLunatiko for help implementing this feature!)

I know in the past I have installed a Cydia tweak from a 3rd party repository that has put my iPhone into an endless boot, which forced me to restore my iPhone and lose valuable data. With the ability to deactivate Mobile Substrate on boot it will solve this problem completely, and overall will make things much more stable on Jailbroken iOS devices.



If you would like to update Mobile Substrate to version 0.9.3997 you will simply need to launch Cydia and refresh your sources. When I went to install this update on my iPhone it took about 15 minutes to completely refresh the sources, so be patient. What do you think about this new feature? Share your thoughts about it in the comments section below.

...So, be sure you have 0.9.3997 or greater of Mobile Substrate (it should be installed automatically when needed, if this is a new jailbreak; the only issue is if you have an old jailbreak that hasn't been updated).

EDIT:

... People should note, however, that doing so will void any warranties you have

Yes.  Be sure to restore your iPhone to Factory Settings before returning it for any issues.