Major Nelson posted more details on the previously mentioned dashboard. Some exciting new features coming down the pipe.
Play from the hard drive: The ability to copy your game to the hard drive on your Xbox. Play right from the drive and save your disk. You will have to insert the disk to confirm ownership though (of course).
Web Access to LIVE Marketplace: Buy downloads from the web and have it download automagically to your console. New maps, TV and movies or even arcade games.
Xbox LIVE Party System: Create a party of up to 8 friends and hang out! Play games together, watch Netflix together (sweet!) or share personal photos. And finally, chat with more than 2 people!
Avatars: Mentioned earlier, this is your personally created character. You can play games with your avatar as well. We’ll have to wait to see more on what that is about.
and new display support: If you use a widescreen LCD computer monitor, you know what I mean when I say “sweet! 1440X900 support!” That’s right, Xbox 360 will do 16×10 aspect ratio. Awesome.
Microsoft Xbox 360 FTW!