who to follow
None so far.
Facebook shows (in a sidebar) a "PEOPLE TO FOLLOW" box with face, name, job title / org, number of friends that are following, and a "Follow" button, e.g. (both Aaron Parecki and Tantek Çelik have seen this particular recommendation when using FB):
Twitter shows a "Who to follow" box in the sidebar when logged in and viewing someone else's profile. E.g.
If you click the "View all" link it goes to a whole page of follow suggestions:
Twitter who to follow page
Here's a screenshot of Kartik Prabhu's "Who to follow" page on Twitter. Note Twitter shows only specified full names in the "Followed by ..." text. This can look interesting when users change their display name for various reasons, e.g. the "⚡️" that is a reference to David Bowie.