MyGeographyNews last fall. I post content and have students leave comments. As you can see, I haven't used the blog in awhile (I know, a very bad thing). Students aren't at the point where they are leaving comments on comments, nor are they writing their own posts yet.
My next step is to get students writing some reflections that can be posted at the blog, then getting their classmates to leave comments. It is slow, but steady work.
photo by: Trinitas Imaging / Udit Kulshrestha