Strange Games has already covered the noble art of Mattress Jousting (two players hold their mattresses then run at each other, ideally in a narrow corridor. But the humble mattress has more to offer if you want to have some strange fun. Consider Mattress Running: a game that everyone should try at least once..simply place your mattress upright and tight to a wall, take a run up and hurl yourself at it as hard as possible. Points can be awarded for style, daring and the lack of broken bones (try the video here for an example run).
But, for truly hardcore mattress running you have to compete in a version detailed in the video below. It's an ideal dormitory game because you are going to need a staircase and as many mattresses as you can get your hands on. Use them to line all the stairs from the ground floor to the top. The aim of the game in the creators' words is "to reach the top of the accomodation, collect a personal item and return to the bottom. Full contact is allowed." As you can see utter chaos ensues. Mass scrummages and crushes in the relatively safe environment of a padded staircase.