MySelf

Are you ready for iOS 5? For unlockers and jailbreakers, custom firmware is your best option.


These custom firmware were made using sn0wbreeze 2.8b8 and will not update your baseband. This is ideal if you need to unlock your iPhone. Even if you don’t intend to unlock it now, preserving your baseband will increase your phone’s resale value.

You never know, right?
Since the jailbreak for iOS 5 is still tethered, you will need to use iBooty 2.3 or redsn0w to boot your device to a jailbroken state. If you’re new to restoring with custom firmware, you will need to pawn DFU your iPhone to allow it to accept custom firmware. Use redsn0w or iREB for this.
Also make sure that you have the latest iTunes 10.5 to restore to iOS 5.

Custom iOS 5 Jailbroken (tethered) and Hacktivated (use this if you DO NOT have the official carrier SIM card)
 
iPhone 4 sn0wbreeze_iPhone 4-5.0.ipsw
iPhone 3GS New Bootrom sn0wbreeze_iPhone 3GS_NBR-5.0.ipsw
iPhone 3GS Old Bootrom (untethered) sn0wbreeze_iPhone 3GS_OBR-5.0.ipsw

Custom iOS 5 Not Jailbreaken, Not Activated (official carrier SIM required)
iPhone 4 sn0wbreeze_iPhone 4_nojb-5.0.ipsw
iPhone 3GS sn0wbreeze_iPhone 3GS_nojb-5.0.ipsw
Note for iPhone 4 and 3GS unlockers:

• iPhone 4 – Gevey Turbo SIM works with iOS 5 as long as you don’t have baseband 4.11.08. If you’re using Ultra, it may not work as furiousmod needs MobileSubstrate to work, and it’s currently broken.
• iPhone 3GS – ultrasn0w 1.2.4 is  ready for iOS 5, the latest baseband that comes with iOS 5 is 5.16.05, and there’s no way to unlock it. However, you can update it to baseband 6.15.00 using redsn0w and unlock it with ultrasn0w 1.2.4. Note that this latest ultrasn0w only supports older basebands.

MuscleNerd also mentioned:

there’s a special “trick” that iPhone3GS owners with baseband 06.15 need for iOS5.  During the new setup screens you see when you start iOS5 for the first time, you’ll be asked about Location Services.  Be sure to select “Disable Location Services” when asked!  Later on in the setup, you’ll have the chance to turn on Location Services again when asked if you want to use “Find my iPhone”.  It’s fine to turn it back on at that point, if that’s your desire (or you can always go in and enable it in Settings.app).