Home Depot or Lowes sells large 8′ by 4′ panels of what they call hardboard paneling. This is very inexpensive at just over $13 a sheet. Oddly enough the surface works just great as a white board. Compare this to a white board of the same size which is around $300.
This stuff is also light enough you can hang it on a wall with double sided tape. Be careful with a painted wall as you can peel the paint off when you pull the panel off the wall. I’ve also mounted these panels with molly bolts.
When I worked at Online Software they had classrooms with the entire front of the classroom paneled with white board. I copied that idea but used this less expensive paneling. We paneled an entire conference room at The Price Club by putting the panels on the wall standing up. We had to cut down some panels to fill the entire wall of the conference room. Have a pile of markers and dry erasers on the conference room table. Anyone can stand up, turn around and start diagramming on a floor to ceiling (8′) white board. Very cool.