Another thing I did, earlier this week, is take a number of smaller sheets of paper, upon which I would draw a map of a room. Each of the rooms had a single door out, a single door in, and an encounter or otherwise interesting content.
Each time the players opened the door to the next room, I would shuffle the sheets of paper and have the person opening the door pick one, in effect randomly determining the order in which they entered the rooms. Eventually, the last room ran full circle back to the entrance.
It was a lot of fun, I was just as uncertain as the players as to what encounter was next.