Steam released the new beta update adding "Big Picture" which turns into into a XBOX360-dashboard-esque thing. I has a built-in web browser, you can hit the "XBOX home" button to open steam in-game menu. It has Store, Library and Community. You can download and install all your workshop stuff, browse gamehubs, browse friends and all that.
To sign up for steam beta, open steam and click "Steam" in the top left, then click "Settings." a new window will appear, under beta participation click "Change" and use the drop down to select 'Steam Beta' and apply. restart steam, and it'll install "Big picture" for you. When Steam launches in the top right will be the button to use "Big Picture."
NOTE: Microsoft XBOX360 controller-Windows USB connector and XBOX360 controller suggested. (otherwise its pretty pointless.)