Instructables user Britsteiner has posted a great HOWTO for making your own gigantic reusablke vinyl wall-stickers. As the instructions point out, this is perfect for rental places like dormitories or apartments, since you don't need landlord permission and you can take it with when you move.
I tested my sticky stuff on an interior closet wall, and found that my ConTact paper was about as sticky as a Post-It note, if not slightly less. It was almost un-sticky to a fault, which is fine by me, since I don't want to pay for damages on my walls when I move out!) My tape also came up very easily, so I was good to go.Link (via Craft)