There have been rumors of an update to the early Froyo build (aka FRF50) that we've been running on our Nexus Ones, and now the download location has leaked out. You can get it straight from Google here (mirrors here in case it gets pulled), but note that you must be running the FRF 50 build, and you must also have the stock Nexus One ROM installed. From there, download the update, rename it to update.zip and slap it on the SD card. Boot into recovery, and away you go.
Early comments at XDA Developers (along with the small size of the file) indicate that these are likely bugfixes for the original build, and so we continue wait for a full update to be pushed out. Give it a shot, and let us know what you see. [XDA Developers]