A towel. Preferably one soaked in nutrients.
Otherwise....PhakeDoc beat me to it : bring a moleskin and a pen so you can jot things down. Moleskin's are the perfect pocket or purse size and you can organize your thoughts on a program post interview and keep them all in one spot. Phake.... nice taste 🙂 I'm addicted to those little notebooks. Talk about something that's just designed to fulfill its purpose perfectly. 😍
I am also bringing along a copy of my essay, c.v. and one of my publications (its unusual, and I expect that it will come up in conversation, and if someone wants to see it, there it is...) but I don't expect to need or use any of these things. I have a purse that's sort of like a little messenger bag, and I"ll put them in that simply because I"ll be bringing a purse anyway. I wouldn't worry about bringing anything else.