Gingerbread 2.3.6 update notification popped up on my Nexus One last night. Well to be honest, I am not sure when the notification arrived since I had not used the Nexus One for more than a week. According to the message on the Nexus One:
This OTA update will upgrade your device to Gingerbread 2.3.6. It contains important bug fixes and security updates.
Initially I was not able to update the phone because the internal storage was somewhat full. I had to move some applications to the SD card and uninstall some of them.
A quick query on Google, apparently some Nexus One owners are getting the update within the past week.