An HTC Desire update has just been made available OTA. The update, version 2.29.405.2 is only going out to users of the unlocked devices and it's currently unknown when it will be coming to the carrier versions of the devices or what regions in which update is available.
The update comes in at 28.87MB and you will need at least 25MB of internal storage free to download and install. We currently are also unaware of what exactly is updated, hopefully it's a preparation for Gingerbread? We sure hope so.