I tried the unreleased beta before valve shut it down.
The actual steam community site will be at http://www.community.steampowered.com
The site isnt up yet but thats the url steam gave me.
Here is some screens that some managed to take before it was shut down:
Ability to open steam while in game (Even 3rd party games)
New settings screens:
Also steam has the ability to add non steam games to games list:
Peek at the new Friends list:











