Nexus S : how to update to the Nexus S to Android 2.3.3

Android Police has published a detailed procedure to manually upgrade the Nexus S to Android 2.3.3 : Google Releases Android 2.3.3 Update .ZIPs For Nexus One And Nexus S

A detailed procedure to manually upgrade the Nexus S to Android 2.3.2 is also available on Android and Me : Update your Nexus S to Android 2.3.2

For those wo have a rooted Nexus S, the reference is on XDA-Developers forum : [REF] Nexus S Guide to Roms, Themes, and Kernels