If you have to just modify the iPhone 3G baseband to 2.28 without updating the firmware to 2.2 or 2.2.1, this is the easiest method to follow! The main reason for only upgrading the baseband to 2.28 is to achieve software unlock and still preserving all the jailbreak apps and appstore apps on the iPhone 3G. This has nothing to do with downgrading the baseband from 2.30 to 2.28 though.
Steps required in order :
1) Download ICE2_02.28.00.eep, ICE2_02.28.00.fls, BBUpdaterExtreme from this rapidshare link

2) Make sure your iPhone 3G is jailbroken and …

Such a wonderful feat, a blessing for all those who accidentally updated their iPhones to 2.2 (2.28 baseband). Dev Team hinted a 2.28 unlock in a screenshot released today boasting the ever popular 2.28 baseband unlock. Please STOP buying x-SIMs from China and look out for the real deal on Cydia : today (Dec 31st) at 11:59 PM EST. All the iPhones in the world released to date are unlockable via a software means and please refrain from buying software unlock from any website since Dev Team intends it to …

Short and sweet! The software unlock software codenamed yellowsn0w is first uploaded to the iPhone and then it is run via OpenSSH on a Mac, simple huh! Even simpler is the fact that it takes less than 8 seconds from running the software to actually seeing the new carrier’s signal! This functionality will be neatly packaged into an App which will be available on Cydia this New Year’s eve. Merry Christmas everybody!

UPDATE : Software solution now released!
UPDATE : iPhone 3G 2.28 baseband is unhackable, all x-SIMs in the market saw a miserable failure (I have tested some and all of the rely on a IMSI spoof which was broken with 2.28. Buyer beware!
It is time for iPhone firmware 2.2 accidental upgrade users! Though iPhone devs have been hard at work chasing 2.11 baseband (they claim to have the unlock solution for 1.45, awaiting a 2.11 downgrade and a simple to use GUI). A much anticipated date of around Christmas for the …

If you are a legit iPhone customer (ATT, Rogers,…) and are looking for 2.2 firmware which preserves unlock capabilities but need a pre-activated unlike pwned and activated firmware, this is for you! Not a legit iPhone user? Follow this post instead.

iPhone1_2_2.2_5G77_Custom_Restore_ATT_1K.ipsw.001
iPhone1_2_2.2_5G77_Custom_Restore_ATT_1K.ipsw.002
iPhone1_2_2.2_5G77_Custom_Restore_ATT_1K.ipsw.003

Requirements :
Legit iPhone plan
Pwned iPhone firmware 2.1 (You may restore to this firmware only from an already pwned 2.1 firmware)
Download this program (freeware) to join this firmware file
Desire to chase the extremes of iPhone productivity!

Features :
Root Partition 1000 MB
Cydia, Installer
Not-Activated (For legit iPhone users!)
Factory default Apple logos (No pwnapple!)

Note : If you are planning on using Gevey SIM, please take a quick peek at this marathon race into chasing the mystery behind Pwned iPhone 3G 2.2 and Gevey SIM issues.
This custom pwned firmware version 2.2 has the older Baseband, Factory default logos (No Pwnapple at boot!) , Pre-activated for non-ATT users, Root Partition size 1000 MB, Cydia and Installer as a bonus to make life simple!

Recommended Steps :
Pwn your iPhone 3G when at firmware version 2.1 using QuickPwn 2.2 either using Windows or Mac(STRICTLY REQUIRED)
Now, download this Custom …

Update : Dev Team confirmed the release date for Software Unlock. Please steer away from x-sim unlock techniques. 2.11.07 is the best baseband for now. 2.28 baseband users : solution pending.

Apple’s iPhone 2.2 Firmware certainly sports some cool new features but is it worth taking the risk and updating given the fact that it disrupts the ONLY available unlocking technique ( Sim Unlock ) ?

I have some iPhone 3G’s (bought from Canada) at my disposal and I first updated one of my iPhone 3Gs directly to firmware version 2.2 since I …

The source of these links : iPhone Devs.
Click on the links to download the files using Rapidshare if Torrents are not your thing’!

Quick Instructions will be posted soon :
PwnageTool 2.2.1 ( Mac )
QuickPwn 2.2 ( Mac )
QuickPwn 2.2 ( Windows )

UPDATE : Jailbreaking 2.2 Firmware was made possible again by iPhone Devs and if you want to download custom ipsws, click here or you can download the jailbreaking tools here.
UPDATE : The overall experience is lot smoother and a lot lot snappier (SMS, Safari,…), fewer Crashes and One Word : Well worth it but I still suggest you to hang in there for the 3G Software Unlock which is due (If you need it that is!).
As anticipated, Apple dropped a major iPhone firmware update v2.2. True to the rumored features, …