With a warning right up front that this solution does fine for single or double works per panel but will not give a tremendous amount of lineage for a group show, I suggest you look at cheap, hollow-core doors. They're light, make very presentable hanging walls for shows and can be stacked or even used for shelving when the show is over. They come in Birch or Mahogany veneer most of the time (but can sometimes be found as primed hardboard) and are often inexpensive at surplus home supply stores. Minimal expense, minimal futzing around and clean, good looking backdrop for the work. I've found that by hinging them together or even a simple nail-through one into the edge of another in two to four door sections gives a good divider for the room and results in a fairly stable, freestanding unit.