All excellent coaches, but only one person on the list is totally in the clear, two can not be hired, one is a question mark.
Petrino: No major college administrator (particularly in the SEC) will touch him this year. Noone is judging him on his personal issues, but he brought that ish into the university by hiring his squeeze. This exposed the university to several wicked lawsuits, which most university presidents will not brush off. He can't be touched. Period.
Tressel: Can't be hired without fear of additional NCAA sanctions, which they would not announce until after you hire him. Can't be touched. Period. Move along.
Davis: Innocent so far, but noone is sure he won't have further issues down the road. I have not seen or heard of any official NCAA pronoucement of his innocence yet. Until then, I'm not sure. I would probably not have qualms about hiring him -- after due diligence, of course.
Fedora: No known issues. Hire the man.