Are there any telltale signs that an academic job interview went well (or badly)? I am currently in the agonizing period shortly after an academic job interview at a regional research school and I'm trying to analyze the day to estimate my chances of getting an offer. 

Overall the interview seemed to go well. The talk was fine and the one on one interviews and meals seemed to go smoothly. But, I wonder how much of that has to do with my interviewers just being nice people. 

Are there any people here with experience - on either side of the interview process - who can provide any feedback about how the interviewers might behave before they do (or don't) ultimately extend the offer? 

If it's relevant, I happen to know I was the last of four finalists invited to campus and it's been at least two weeks since another candidate was interviewed.
Even if a department loves you, it's unlikely they'll show any overt signs (especially in an official capacity) because they want to maintain a reasonable negotiating position. 

But individual faculty are not always "with the program". For example, it's happened to me that someone said (during an interview) "I really like your profile and will be making a strong case to make you an offer". But while this might be flattering, it also depends on how much power that individual has over final decisions.