Is it appropriate to include class presentations in CV? I have just earned an MA degree in a social science field. I'm planning to apply to American PhD programs (sociology). I'm from a developing country, and my university is quite modest, if not godforsaken, no extracurricular activities, no interest in research. My CV is quite empty. All I have is the  B.A. and M.A. degrees (I'm ranked first in both of them, if it matters), plus a B.A. thesis and an M.A. one; both of which are, I believe, worthy of publication.

I used to jump at every class presentation opportunity in my B.a. and M.A., sometimes in front of more than 100 classmates, at other times around twenty (M.A.). Sometimes, I used to spend half of the session presenting and leading the discussion, sometimes the whole two-hour session.

Is it appropriate to list these presentations (+10)? If so, in what format?
I feel your CV is already quite strong based on the fact that you have topped in both the mentioned bachelor and masters degree. Adding this detail in the achievement section would be sufficient to make the CV look strong.

However, I feel that presentation and discussions are integral part of the degree in Arts itself. So, by adding these details (which are trivial in some sense) would not help much. However, you could probably mention something in your strength section of CV under "Presentation skills", "Discussion skills". You don't have to mention the topics that you have presented, as these would look like junk to some people.