I submitted a few letters of interest to some of the schools I was waiting on. I did recieve an interview at one of the schools, Georgetown, but I do not know if this was because of the letter or they were planning on interviewing me. I called each of the schools and asked whether it would be ok for me to submit a letter of interest/update letter. I then looked on the website to see who the dean of admissions was. I decided I would rather send the letter to the dean of admissions rather than the admissions committee, bc if its sent to the committee it gets added to your file, but nobody may see it until its too late. If you send it to the dean, he may or may not look at it, and it still gets added to your file, so there you have a chance of actually someone seeing it. Mine was structured of what I did this past summer, what I will be doing before matriculation (I graduated and am taking a year off), how that ties into my interest in the school, then wrote why the school is a great fit for me, and then I ended it with asking them to consider me for an interview. I wrote it as a professional letter. If you have any quesitons, let me know,
Also wends, I believe everything you sent in gets added to your admissions file, so I personally chose not to address it to the admissions committee also