Just a quick post to tell you how to update your Nexus One to Android 2.2 Froyo immediately without waiting for google to send it to you OTA.
Download this file from google’s servers: http://android.clients.google.com/packages/passion/signed-passion-FRF50-from-ERE27.1e519a24.zip
After that just follow the below mentioned steps:
Put it on your SD card and rename to update.zip
Power off then hold trackball and press power again to boot into recovery
Go to Bootloader -> Recovery
Press power button + Vol. Increase
Apply the update