drlexygoat, my interview invitation came in the mail in a big, white envelope (thick too).
They send you two computer CD's (one about NSU and the other about the College of Osteopathic Medicine), a copy of the COM newsletter and a bunch of papers. The papers contain instructions on how to get to NSU, hotel info, etc., a list of students that have volunteered to answer questions and to house applicants, and two forms you have to sign and return: a dress code/attendance policy form and a OMM form. Basically the forms state that you understand and will abide by the dess code and attendance rules, and the OMM form states that you understand that you will be touched by other people in the process of learning OMM.
Good luck! (and wish me luck too!)