Official ICS Firmware for Samsung Galaxy S2

I9100XXLPQ (Official Final Build) Base Firmware: I9100XXLPQ (4.0.3) Build Date: 9th March 2012 Modem: XXLPQ CSC: OXALPQ Change List: 223505 Kernel Version: 3.0.15 DOWNLOAD MD5: 013D99661014CCFF2404C273D70D21 2D (Thanks To SamMobile) (DO A WIPE BEFORE FLASHING!)

Stock Kernel:

Download (.TAR) MD5: 7C1ACDE0CC8A221746EBEF2F6975FA 04 (Thanks To Intratech)

Stock Modem:

Download (.TAR) MD5: 223BD8B9B2B67AF8E12DA88B32E929 63 (Thanks To Intratech)

Chainfire's CF-Root XXLPQ (Rooted Kernel - Thread): DOWNLOAD (Thanks To Chainfire)

Instructions For Flashing ICS: - With 1 File In The Package:

Extract the firmware Open the included Odin Put your device into Download MODE (Home + Volume Down + Power) Click PDA and select *.tar.md5 Then finally click START!

-With 3 Files In The Firmware Package:

Extract the firmware Open the included Odin Put your device into Download MODE (Home + Volume Down + Power) Click PDA and select I9100_CODE_*.tar.md5 Click PHONE and select MODEM_*.tar.md5 Click CSC and GT-I9100-MULTI-CSC-*.tar.md5 Then finally click START!

Instructions For Rooting ICS :

Extract the Rooted Kernel Open the included Odin Put your device into Download MODE Click PDA and select CF-Root-SGS2_*-v5.3-CWM5.tar Then finally click START!

* Varies to the Firmware you downloaded.

REad more and screenshots available at..
Source: http://forum.xda-developers.com/showthread.php?t=1544487