Until we get the press release from Microsoft you can check out all of the details over at Major Nelson
There are two levels of the for the 360, one at $299 and the other at $399. The basic one at $299 which includes the base system, a wired control, face plate, and standard AV cables. For an extra $100 you get a 20GB hard drive, wireless controller, headset, remote, and HDTV Cables.
To be honest I'm really disapppointed. To make such a big fuss over the new system being HD and not including the HD cables with the base system is pretty lame. Then there's the decision not to include a HD with every system which means that there's no incentive for developers to even code for it which means that it's a lame duck purchase unless you really want to play MP3 files and other things through your Xbox360.
Pricing for the accessories was also released. You'll have to plunk down $99 for the wireless networking adapter, $40 for a 64MB memory card, $20 for new faceplates, and $40 if you want to get a VGA adapter for your 360.