There is a user here on the site whom I'd like to contact about something entirely unrelated to Drupal - he lives in/near my hometown. Is there a private message system or an email system? I looked on his profile but could not find anything.
Stack Exchange doesn't provide any way to contact user privately, except via a chat room you create, where the only users who can enter are the other user and you. (The chat room needs to be set like that, or it will be accessible from every user.)
Keep in mind that chat moderators can always enter rooms to which other users don't have access.
Alternatively, if they show their email in their profile, you can contact them using that.