Best Buy has the Xbox 360 HD DVD player accessory for $49.99.
This item sold out when Amazon listed it for this price earlier today, as you still can get the free 5 movie promotion found here. In addition, it comes with the movie King Kong and the universal Xbox 360 remote. Even works with PC's via USB.
Secure the deal and save on shipping by checking availability and choosing 'in store pickup'. Shipping comes in at $4.99 if sold out locally.
Check it out: Microsoft HD DVD Player for Xbox 360 