[Nexus S General] kenvan19:
I updated the OP's steps for 2.3.3 and posted them here as well as in a new thread

Warning: If you break your phone trying this, I am not responsible. I do not guarantee that the following is safe or that the steps are correct. Rooting your phone voids the warranty. I have no responsibility for anything that occurs as a result of your following these directions! I cannot provide any support nor guide you in undoing this process and restoring the phone to factory condition.

This process will wipe your phone. Ie, you will lose all your apps/data on your phone and have to reinstall them. It will also wipe your external storage, so back that up prior to proceeding if you want to keep anything.[/B]

1) Download the "androidsdk.zip" file from here: Android SDK

1)a You'll need to install the SDK, you'll find instructions on how to do that on the link above

1)b Also download this file and unzip it to your desktop.

Unzip the SDK file (if not already unzipped automatically upon download), and place the "androidsdk" folder on your Desktop. It has to be in this location for the rest of the steps to work.

1)c Download the newest Recovery from here (find Google Nexus S its near the bottom) and place it in the folder "adb-fastboot" on your desktop

2) On your phone, go to Menu>Settings>Applications. Select "Development" and check the box next to "USB debugging"

3) Connect the phone to your Mac via the USB cable

4) Open a Terminal window on your Mac (Applications>Utilities>Terminal), and copy/paste the following into the Terminal:

~/Desktop/adb-fastboot/adb reboot bootloader

Hit "Return" and wait for your phone to to reboot into Bootloader/Fastboot mode

5) If your Bootloader screen says "LOCK STATE - UNLOCKED" then skip to Step 6. If it says "LOCK STATE - LOCKED" then copy/paste the following into the Terminal:

~/Desktop/adb-fastboot/fastboot oem unlock

Hit "Return" and on your phone will prompt you to confirm and warn you that you are going to lose everything. Confirm. At this point you will have an unlocked bootloader.

6) Copy/paste the following into the Terminal window:

~/Desktop/androidsdk/tools/fastboot boot recovery-clockwork-3.0.0.5-crespo.img

Hit "Return" again and wait for recovery to boot.

For the following steps while in Recovery, use "Volume Down" to highlight a selection and "Power" to choose that selection:

8) Choose "mounts and storage"

9) Choose "mount USB storage". Your phone should now be mounted on the Mac as a Device called "NO NAME"

10) Download the superuser file here and place it on your SD card.

11) Eject/unmount your phone in the Finder on your Mac.

12) On your phone, choose "Unmount"

13) Choose "mount /system"

14) Choose "+++++Go Back+++++"

15) Choose "install zip from sdcard"

16) Choose "choose zip from sdcard"

17) Choose "su2361ef.zip"

At this point you have root, but your phone will continue to replace ClockworkMod Recovery on reboot. To prevent this, do the following:

1) Reboot your phone, and download the app "Root Explorer" from the Market

2) Open Root Explorer and navigate to the "etc" directory.

3) Tap on the gray box that says "Mount R/W"

4) Tap and hold on the file "install-recovery.sh" and rename this file to "install-recovery.sh.old"

5) Download the app "ROM Manager"

6) Open ROM Manager and choose "Flash ClockworkMod Recovery". At this point you are all set :).