Valve Opens Wide, Delivers (Strangely Familiar-Looking) Steam Community Updates
Day 1 saw the announcement of Game Hub, which includes user-generated and moderated content, forum-like capabilities, news, and more.
Day 2 - Group updates
On Day 2, Steam announced Group updates. Basically, Valve wanted to make it as easy as possible to create and view Groups, and each Group now has its own discussion area (i.e., a forum) that facilitates both public and private conversations. Users can also list their favorite groups on their profiles so others can see and possibly join in themselves. (That sounds an awful lot like Facebook groups.)

Day 3 - User content updates
On Day 3, Valve announced updates to user content; specifically, all manner of your user-generated content are all accessible right from your profile, users can add anyone’s items as Favorites to find or share them later, and users each get an image wall on their profiles to collect their screenshots in a tiled format. (That looks an awful lot like Windows Phone tiles.)

Day 4 - Friend activity
The final announcement for Day 4 is about friend activity. The other updates are centered around more public displays of gaming achievement and debate, but now you and your friends on Steam can hang out in private. Users will get a feed of items upon which they and their friends can interact on various posts, and you can post a status update on your profile, too. (Er--yeah, that’s just Facebook.)
Unfortunately for all but 50,000 lucky Steam users, all of the aforementioned goodies are currently only available in beta for those who have achieved the Pillar of the Steam Community badge.
As a consolation/teaser, though, anyone can access the Team Fortress 2 Game Hub (and the new Mann vs. Machine game mode) as well as the New Steam Community Beta Group.
Oh, and Portal 2 Puzzle Maker so users can make and test out co-op “test chamber”. With that, we’re pretty sure that’s all the Valve news for now.