Froyo madness never ends. It seems that a new Android 2.2 OTA update is being pushed out for both AT&T and T-Mobile Nexus Ones today. We don't have a lot of detail yet (we haven't even taken time to load it -- wanted to get the word out ASAP), but supposedly this addresses some security concerns. It's another very small update (900k) and if you can't wait for it to come OTA you can grab the update direct from Google HERE. Install it just like the others, and remember you have to be using a stock recovery.
Update: Thanks to LoxDev rooted users can get in on the FRF91 fun too. Hit HTCpedia to find links and instructions to download and flash FRF91, root for FRF91, and CyanogenMod 6 kernel and developer tools for FRF91. Remember, standard warnings apply -- do this at your own risk.