A simple curtain rod with two or three full size sheets in a neutral color like beige or tan across the area will work. I have done this two different times. You will probably need more that one curtain rod so you can add extentions. a tension mounted one would work if it is between walls. hang it as high or low as you want, but highest is better looking. Sheets are longer and cheaper than curtains, but if you get them in the colors I suggested , they will look like curtains. Make sure you use enough to drape like curtains,so it doesn't look like a sheet is stretched across the area. measure length you will need, and hem the rest to make a rod pocket. I used tan sheets in a house that had windows too big for curtains. I used a rod that looked like iron and black curtain clips instead of using a rod pocket.No sewing what soever was required. When I sold the house the buyers insisted that I leave the curtains. If the your son's curtains will be opened and closed alot, the rod pocket would be best.

Hi coolmom,
I would suggest haunting thrift shops or auctions (or IKEA) and getting a few tall book cases or wardrobes ... he probably needs the storage anyway. You can screw them together (facing in to his room) to make a "wall". If you connect them in an "L" shape with the entrance to his room by the laundry door he will have more privacy, and the "L" will provide better support since wall attachment is not an option. Second-hand office furniture stores could also be a good source.
Hope this helps!
Baer

Thanks for the great ideas. We may create a room divider using a combination of bookcase and curtains across the 12' room. Thanks again!

You could place a bookcase or two on each side and then place the tension rod with the curtain between them. Also the backsides of the bookcases can be decorated with posters, message board, etc.

Looks like he could use some closet space too, so a couple of armoires would fit the bill, and reduce some of the noise of people clattering down the stairs. You can find some cheap ones on Craigslist. Search for armoire or wardrobe cabinet. If the ugly back bothers anyone (and doubt boys would care one way or the other) he could starch some fabric across the whole group of room dividing furniture.