The Froyo (Android 2.2) OTA update for the Cellular South HTC Desire is approved and on the way. According to Cellular South's Facebook page, users should receive notification of the OTA update "over the next few days", and some phones will be able to manually check for the OTA by midnight tonight.
To manually check your Desire for any available updates, simply press Menu > Settings > About Phone > System Software Updates > Check Now. A larger overview, and a full explanation of what to expect can be found at the source link. Froyo really breathes new life into the Desire, so Cell South users are in for a real treat even if it is a bit late. [Cellular South Discover Center]