Gingerbread 2.3.3 is at long last available for Nexus One, even though the OTA is expected to go out over the next few weeks. But if you are impatient like me, but yet still holding on to a stock Froyo 2.2.2 on the N1, download the update package from
Follow the instructions at https://studiohub.wordpress.com/2010/05/23/manual-android-2-2-froyo-update/ if you need instructions for the update. Gingerbread takes about 10 mins to patch. Patience~!
[OH NO~!]
If you get the following error
assert failed: getprop(“ro.bootloader”) ==”.35.2017″ || getprop(“ro.bootloader”) == “0.35.0017″
E.Error in /sdcard/update.zip
(Status 7)
Installation aborted.
You’ll need to update the hboot. Grab the hboot update package from http://android.clients.google.com/packages/ota/passion/d6096cac5e9f.signed-hboot-0.35.0017.zip, update as per normal, then do the 2.2.2 to 2.3.3 update.
Screen may flash and system reboots a few time, be patient. Yes it is a long additional 3 mins of darkness as the hboot updates.
Source: pwoz from nexusoneforum.net (http://www.nexusoneforum.net/forum/nexus-one-google-phone-news/10576-nexus-one-getting-ota-gingerbread-update-next-week-16.html)
And we have Gingerbread after an agonising 2 month wait. Now for Ice Cream Sandwich… Next year maybe…
[Update] 
1. First look. Nice green theme.
2. 3D drawer from Launcher Pro acts erratically. Turn that off.
3.I like the glow that marks the end of the scroll.
4. Under Apps, there is a new shortcut “Downloads” which takes you to recent downloads.
Zonghe's Blog 
where can i download froyo 2.2.2?
If you are using Nexus One you should be having Gingerbread by now. If you are using some other phones, the do check out xda forums for custom builds.