Steam’s updated Community functions are now out of beta and live for everyone. If you use Steam it’ll probably ask you nicely to update the client, but otherwise it should be smooth enough to log in and take a look at all the new features.
They’re detailed in full on this ‘Community content‘ page, but as a broad summary every game now has its own ‘hub’ page in which people can share things like mods (through the Steam Workshop) and screenshots. It’s possible to ‘vote up’ favourites, so you can probably look forward to a spate of My Little Pony mod images on the Skyrim page until the community figures out how it wants to react to that.
Every game hub has its own forum for discussing the title.
All of your screenshots, video and mod work will now be grouped together on one page, accessed through your profile. There’s also a new “interactive feed” to show you what people in your friends list have been up to lately.