The boxes for Xbox 360 games will resemble the current Xbox generation boxes, green DVD cases with a paper cover insert holding the Xbox 360 logo.
Here's a list of accessories that were displayed:
IGN was a bit surprised by the size of the Xbox 360 HDD in accessory form. They say you actually have to buy the entire top part of the console, rather than a little attachment. More details at IGN
Wireless controller Memory Unit (includes case) Rechargeable Battery Pack Play & Charge Kit Quick Charge Kit Wireless Network Adapter Hard Drive Universal Media Remote S-Video AV Cable VGA HD AV Cable Component HD AV Cable Face Plates