There has been some discussion on this, but it is fairly tangential. Is it possible to get the Assignment module to support multiple submissions? In concept this would be more like a "Journal" (see the discussion "Death to Journal) in which students could "submit" work to teachers whenever and as often as they'd like to. I really think that this is a useful feature that Moodle lacks, because on the most abstract level it's an open communication channel between student and teacher (as opposed to the more structured "assignment", "survey" and "chat" channels).
I thought that this might have already been implemented under the guise of another module, but if it is, I can't find it. Either way, I think it would be a valuable addition to Moodle.