Back in school we first learned of Homasote Fiber Board. It covered all the walls of our crit space and was used as a surface for presenting our work. A friend's recent at-home project using Homasote as a pinup board reminded us of this great versatile material.
It comes in 4'x8' sheets, much like gypsum board, plywood, and other building sheathing materials. However, the completely tackable board is much lighter in weight than gypsum board. It's 1/2" thick and is even weather resistant. Fix it to wall framing with nails and even bend it as long as the radius isn't too tight.
We've generally seen the boards wrapped in fabric to give them a more finished appearance but they can simply be painted, too. And, best of all, Homasote is a green material that's made of recycled newsprint.