HOMASOTE.... Available at most larger building materials centers. "Green" product (actually grey), made from recycled paper. Smooth surface that takes and holds pins really well (IMHO much better than sheetrock).

[link]http://www.homasote.com/about.aspx[/link]

Comes in 4x8' sheets. Shorten to the length of your board (save for a small portable work surface), then split to two pieces 2' wide x length of board. Use one now, save one for later or share w/ a buddy...