How to mount a white board on a wall without making holes in the wall?
I have had a lot of success with those "Command" adhesives from 3M, but it entirely depends on how heavy it is.  If you are not familiar with them they have a tab that allows them to break their glue bond by stretching the material and I have not had any leave marks on the wall.  They are available at about any hardware store.  They have a weight rating on the package and I would figure half that.