I have been spending a good deal of time considering this as I am wait listed at my top two schools and rejected everywhere else (which is actually not as terrible as it could be, I guess). At this point, I'm feeling that it's Hail Mary time. I am definitely going to send a note to the DGS at both schools. I am going to visit one school during my spring break and two professors have agreed to meet for coffee even though it is their spring break! So I'm going to write to the DGS letting him know who I met with, what we talked about, etc. In my note to the other school, I'm going to indicate how my studies are progressing (my senior thesis, etc) and that I am incredibly interested in going to their school.
I feel your pain. The wait list is a confusing place to be. The best advice that a professor has given me is to be enthusiastic, don't disappear, but don't be pushy. Hope that helps! Good luck to everyone.