The Framsta glass panels from IKEA are supposed to go behind the TV. We discovered they make great whiteboards when simply hanged on the wall.
To hang the panels ask for these mirror clamps at the IKEA spare parts desk. Back home, mount them on the wall in the right distance.
Now put the panels in.
And: You're done. In addition you can use binder clips or something similar to hang things like concert tickets or bills on the panels.
Remember: Always use some non-permanent whiteboard markers (don't ask...)