You can now follow other people by hovering over their name (or on the profile page)

When you hover over a username (on a comment or story) - it will show a little dialog which lets you follow the user:

This will also show on your profile and the person you followed will be notified on the little bell icon at the top navigation bar. The plan is to make a home feed tab to keep track of what the people you follow are doing The same applies for communities!