another curtain room divider idea. this one is from marc who used lightweight muslin with the kvadrant curtain rail system. i can no longer find it on the ikea site, but i think the ikea kvartal may work the same.
adding to marc's idea, if you choose not to use fabric, you can also try ikea's curtain panels to divide a room. may not be as cheap, but they are pretty good looking.
other room divider ideas: