In my previous blog I already provided the way by which you can install 2.3.3 on your Nexus S.
Its 2.3.4 now.
Google today announced Android 2.3.4 would be rolling out for the Samsung Nexus S in the coming weeks.
If you're a Samsung Nexus S owner, you can hit the link below -- download the update and install Android 2.3.4 manually. Here are your instructions:
Download the file from Google right here : http://android.clients.google.com/packages/ota/google_crespo/a14a2dd09749.signed-soju-GRJ22-from-GRI40.a14a2dd0.zip
1. Place it on the root of your external storage
2. Shut down your phone, and reboot into the bootloader by holding volume up and powering back on
3. Use the volume buttons to choose "recovery" from the list, and select it with the power button
4. When you see the triangle on your screen, hold power and then press volume up and you'll have a list of options, choose the file to update
Wow you are done....
Now you can use Gtalk with voice and video right from your phone ;)