fA few ideas -
Carry a professional bag (guys too) a computer carry case might work.
In the bag, carry:
Kleenex,
A portofolio with CV, paper, pens
a shoe shine cloth for last minute scuff removal
breath mints
enough cash in small denominations for snack/drink and transportation
small bottle of water
small paperback book to read
cell phone TURNED TO SILENT
lotion if your hands get dry or gross (gotta shake hands and not be creepy)
In your suitcase remember to have all the normal stuff plus:
Undershirt (not a tank top, nervous sweat stains are ugly)
shoe polish
travel iron (if not staying in hotel with one)
small gift for host (if staying with med. student)
thank you cards (write these on your way home before you forget)
stamps
cold weather wear if travelling somewhere colder than you are used to
To reiterate what a previous poster said - do NOT check your suit and shoes!! The airlines will usually hang these things in the captain's closet if you ask the flight attendant nicely.
anything else?