stack of $1 bills, passport, photocopy of passport hidden somewhere else (in case your original gets stolen). Phone numbers, addresses, and printouts for any reservations you have.
The $1 bills are for hotel tips, taxi fares, and a bunch of other places where all you might have is a $20 and no one seems to have any change.......
One of these maps, if you have time to get it:
Can-Do Maps and travel guides
Rich