Xbox 360 Memory Unit
Retailing at $40, the 64MB memory unit allows you to save your games (provided you're not using the hard drive) as well as your Live gamer profile. And, though full details haven't been announced yet, most Xbox 360 kiosks have a slot for the memory unit that will allow you to download special content to use on your home console.
Xbox 360 Wireless Network Adapter
For those with a wireless network in their home, the Wireless Network Adapter will allow you to bring your system onto your network. In addition to playing games on Live, you'll also be able to hook your 360 into your media center to transfer movies, music and pictures from your PC to your 360. The adapter supports 802.11b, 802.11g, and 802.11a.
The Wireless Network Adapter retails for $100.
Xbox 360 Play and Charge Kit
For the times when your batteries are running low and you're in the middle of a game, the Play and Charge Kit lets you plug your 360 Wireless controller into your 360, giving it just enough power to make it to the next level.
The Play and Charge Kit retails for $20.
Xbox 360 Rechargeable Battery Pack
Another power solution for those with wireless controllers, the rechargeable battery pack allows up to 25 hours of gaming on one charge.
The Rechargeable Battery Pack retails for $12.
Xbox 360 Custom Faceplate
One of the more unique aspects of the Xbox 360 are the custom faceplates. The plates can easily snap off the system (similar to a cell phone's custom faceplate) and can be replaced with all kinds of designs, giving your system that added bit of flair. About five designs should be available at launch, including one with flames painted on it, one with a wood grain finish, a silver one and a blue "Hot Rod" design. As the year goes on, expect other companies to make special plates available, including ones with licensed characters or special features.
Custom faceplates retail for $20.