This Xbox 360 HD-DVD drive was the first HD-DVD player to support 1080p output, albeit only over the Xbox 360s VGA output. With the release of the Xbox 360 Elite and the addition of an HDMI output to new Xbox 360s, you'll be able to get 1080p output on your TV over HDMI. This drive can also easily be hooked up to your PC to get HD-DVD playback.
The Xbox 360 HD-DVD add-on was released in November 2006 and retails for around $180.