THIS WORKED ON MY AT&T SGS2, HOWEVER, I ASSUME NO RESPONSIBILITY IF IT BRICKS YOUR PHONE.
What is needed:
1. Download kernel from codeworkx here
http://forum.xda-developers.com/showthread.php?t=1285823
2. Download SuperOneClick v 2.1.1
http://forum.xda-developers.com/attachment.php?attachmentid=674200&d=1312258565
3. Odin 1.82 (Search Forums)
4. Android drivers for your phone install using Kies.
http://org.downloadcenter.samsung.c.../20110512115717796/Kies_2.0.3.11082_152_4.exe
Now we are going to flash the Kernel(might be a few mapping issues, but I havent noticed any yet)
1. Power off device.
2. Hold down both vol down+vol up and plug in usb cable
3. Hit volume up and accept warning
4. Open odin
5. Choose the kernel you just downloaded and load into PDA.
6. Click start and let it run completely and boot up.
7. With phone booted make sure you have usb debugging checked and plug your phone back in.
8. Open Super One Click and click root.
**It will hang up at #6 of Super One Click when it does this unplug your phone go into settings uncheck and check usb debugging again then plug back in. At this point it will continue with the root. It will send a test to your phone and you may or may not have to click allow for Superuser.**
*Try this if SuperOneClick fails. I have not tried this method. It was originally posted by Paulyyhoffman here . If it works for you please let me know. **
Alternate Root Method with Clockwork Mod
Download file here and flash in CWM.