I know of at least 2 programs that won't send out invites until sept, late sept. Also, when I submitted my app, I did so "late"' like mid August. So I called all the programs to tell them I had just submitted it. Really it was my way to say, "Hey, here I am!" And I got an interview invite from all of them by the end of the week, and the invites started rolling in the next day! So if you have a late letter, or submitted late, or whatever, a friendly call to a program is fine. Also, as long as they are done professionally, repeat calls can show a program that you are highly interested in them, and can be helpful to you. Just don't be annoying, cuz no one likes annoying, and seriously, one call is not annoying, so don't worry. Also, avoid malignant programs. You can tell when you interview, they are the programs with fellows that are elusive when asked about things pertaining to program, unhappy looking fellows, etc. Or just ask around to other applicants. Matching to the wrong place means years of potential misery.