I was talking to a post-doc fellow at my Hopkins internship today, and she was saying that most schools will pay for your interview travel expenses. I hadn't heard that before - is that something that happens often?
I got money everywhere I interviewed at in 2007. It varied from a hundred bucks to almost three hundred (I think they had some money set aside, and then distributed it to however many people came for interviews). One place put me up in a hotel for an extra night to catch a flight home the day after the interview.
One of my professors who used to be on the graduate admissions committee of a really nice and competitive clinical phd program said that they tried to make it so that interviewees did not have to spend any money - from the flight, to the hotel (I think they stayed with other grad students), to food, etc.
I went on 6 interviews including some big name schools two years ago and none offered me money. Perhaps they didn't think highly enough of me . I know my program does not offer money for people to come and interview and I really think the practice is very rare!