So you recently bought your Nexus S and found out that the Hummingbird processor was a bit slow for your liking, and you wanted to do something about it? Luckily for you, morfic at XDA has managed to overclock Nexus S to 1.2 Ghz, which I was expecting to happen ever since the Gingerbread flagship device went live.
Warning: Rooting/Overclocking your Nexus S may cause unseen damage to your handset. All of this is done at your own risk and we take no responsibility for any damage you inflict upon your precious Nexus S.
To be able to overclock your Nexus S to 1.2 Ghz you need to have a rooted Stock Android 2.3 ROM, the instructions to which can be found here. Even though the developer has listed this kernel as a Stock Gingerbread ROM only kernel, a daring user tried this on the MoDaCo ROM and reported it to be working just fine.
Hit the source link for installation instructions. This kernel is a work in progress and the developer has expressed intention to bring the kernel for other custom ROMs as well.