The new E3 is more than just talking about games, it's about talking about the changes to the whole console experience.  Here is a list of improvements coming to Xbox Live.

1080p Video content on Marketplace - In the past all the video content on the 360 topped out at 720p but now the move has been made to provide 1080p content as well.  Some more details on this are needed but it sounds good.

Facebook on Xbox 360 - From the video I saw you'll be bale to see your friends profiles, status updates and pictures.  It looks like a similar navigation of the current UI except Facebook will be it's own application to launch not unlike Netflix.

Twitter on Xbox 360 - This will be a new app to launch that will allow you to track your friends tweets and post status updates.

last.fm on the Xbox 360 - I've never heard of last.fm but it is a "social music community" that recommends music based on your listening trends.  I assume this means you'll be able to create custom game sound tracks to listen to while playing.

Avatar Store on Marketplace - This online store will have some free and some paid content for your avatar to wear.  There will most likely be content unlocked by achievements as well.

Netfix Upgrade - There will be some much needed improvements to Netflix on the 360.  You will soon be able to browse the streaming catalog and add movies to your queue. 

Full Xbox 360 Game downloads - You will soon be able to download full xbox 360 games directly from the Xbox Live Marketplace.  This move is very interesting since it will be a direct assault on the brick and mortar retail shops.