In contrast to citizen journalism, this is when the individual isn’t reporting out of happenstance. The reporter, who is not acting as a “professional,” (see below) made a conscious choice to go out and report on a topic. This term was coined by Chris Nolan at Spot-on.com.
Update: These might be called “Placebloggers.” One of my favorite stand alone journalists in San Francisco is N Judah Chronicles. To my knowledge this blog is a passionate hobby, not part of the author’s profession.