As others have probably already said, David Moyes would be the stand-out candidate by some distance. If he is interested in the job, I hope the club do everything in their power to persuade him to join us.
Apart from Moyes, I think Steve McClaren should be another contender if there is any any chance of him being persuaded to leave Derby following their play-off final defeat yesterday.
Paul Clement is an interesting potential candidate, and there will probably be a few rumours now he seems keen to leave Real Madrid and become a head coach in his own right. I backed the appointment of Steve Clarke at the time and think the head coach role suits an experienced assistant, even if they have not been a number one before.
However, I would be surprised if we appoint another assistant and promote them to a head coach due to the poor run of form during Clarke's last few months in charge and also because there are arguably better candidates available this time than there were when we appointed Clarke and when we appointed Pepe Mel back in January.
Whoever we appoint, I hope we move fairly quickly from now. The club have a bit more time to make the right appointment now we are in the close season, but it is vital to get the new head coach in as quickly as possible to give them an opportunity to assess the current squad and have their say on potential new signings.