Excellent news, folks. The boot loader on the Samsung Nexus S can be unlocked just as the Nexus One’s was.

Steps:

Step#1:

Power OFF the phone
Step#2:
Now Hold down volume up + power at the same time


Step#3:

Now you are in the standard recovery mode (wo. looks like Apple Recovery Mode:P)
Step#4:
Assuming you have 2.3 SDK installed with fastboot (Google around for that info..), now on terminal/windows or Windows cmd depending on OS type “fastboot devices” to check your device can be seem via USB
Step#5:
Assuming you device is seen via fastboot devices, now type “fastboot oem unlock”
Step#6:
Accept … and new bootloader is unlocked.

Why would you want to unlock the bootloader? You need access to install a custom recovery. And you need a custom recovery to install custom ROMs. And you need custom ROMs because, well, you just do. Trust us. So this is very good news indeed. If we don’t see custom ROMs by the end of the day, somebody’s slacking. :p

Source:[androidcentral]