Today, Apple team has released firmware 2.2.1 update for iPhone, iPhone 3G, iPod Touch and iPod Touch 2G. New firmware is available for download in iTunes.
As such, there is no major update in iPhone and iPod touch firmware 2.2.1 (Modem Firmware: 02.30.03). It has few bug fixes and small improvements in applications like Safari and Camera roll.
Updates and Improvements in Firmware 2.2.1
So as Dev Team suggested, do not upgrade iPhone through latest update as it will break yellowsn0w. If you want to upgrade iPhone firmware to 2.2.1 then use custom firmware which will not allow the baseband update.
Download appropriate 2.2.1 firmware from given links and don’t forget to backup your device before the upgrade.
Download 2.2.1 Firmware Update for iPhone and iPod Touch
Download iPhone 2.2.1 firmware
Download iPhone 3G 2.2.1 firmware
Download iPod Touch 2.2.1 firmware
Download iPod Touch 2G 2.2.1 firmware
[...] days back Apple team released firmware update 2.2.1 for iPhone and iPod Touch. But Dev Team has strictly warned iPhone 3G users and suggested not [...]