@michaelzhang,
See the remark by Tsarstepan. There is a term invented by the academic hippies in the early 1970s, facilitator.
Facile is the French word for easy, and facility, in some contexts, can mean easy, the ease of doing something. So, a facilitator is someone who makes things easy. Specifically, in the 1970s academic hippy sense, it means someone who makes a discussion easier, or, as Tsarstepan points out, keeps the discussion on track (note that in the text from that page, this joker calls himself a "focus realizer," meaning, i take it, that he helps the group to keep their focus on the subject of the discussion).
So, it's not so much an organizer, as a moderator.