what to do if someone cancels???

Definitely take the wait list interviews if offered and assume that you are on equal footing. The year that I went through the process, I got a wait list interview from Indiana and then ended up on their "ranked to match" list.

I agree boneblaster. I just wrote something about this again on the "Advice from a Residency Coordinator" post if you want to read it. Like it said, there is likely little difference between you and the guy who canceled his interview in the eyes of the PD, you may have just been edged out by something relatively insignificant (we have to make decsions somehow as hard as it is). So if you're interested in the program and able to get there in short notice, go for it. I'm fairly certain we've matched residents who were last minute drop ins. You just never know.