like rob, i use black felt. in my current home i have no room large enough for strictly sewing, so use the dining room for piecing, kitchen counter for fmq on my domestic machine. last home i had large piece of heavy duty cardboard from refrigerater packing box. no Lowes in that town & no insulating foam at local hardware store. i glued the felt to the cardboard & then we attached it to wall of spare bedroom. it would hold blocks w/o pins, had to pin the pieced quilts as it grew during assembly. it lasted for 15 yrs and would still be there if we hadn't moved. i currently have a large piece of black flannel hanging over deck door/windows in my dining room. i put a hem in bottom for rod to hold out straight. i put hem at top, attached those little plastic rings for crochet etc and placed push pin hooks into wall above door frame. out of site and be minimal repair when we move again. it has worked very well for several years now, but i really really like robs idea for portable wall (note #4 above) and will think of some way i can make it work for my house of cubicles. putting it away for dinner guests would not be as easy as taking down my felt panel & rolling it up for the occassional dinner guests or house full of visitors.
...but i'll think of something. thanks rob! such a great idea!!