My buddy Frank Joyce found these new background buildings manufactured by a company called Kingmill. They are made from a cardstock-like material. He drove down today from Kirkwood and brought a few of these and we propped them up on my layout in a few spots. For a more permanent setting, they are supposed to glue to a supportive piece such as insulation foam. $6.00 buys a large "building" or a couple of smaller ones.
I just checked their website (Kingmill.com) and they're available in HO and N. They're called "Radical Flats". Frank ordered his directly off their website. And a correction to how they're to be applied: Don't use white glue. Use a spray adhesive such as the one made by 3M.
Thanks--I was also looking at the website and it appears you can buy as many or few of the related flats as you need for a layout. I can imagine two or more people could purchase several pieces cooperatively. Tom