So I thought, the plaster stuff was sooo messy, took soooo long to do, and the plaster material was toxic (so had to wear gloves, goggles, breath mask, etc), and so forth. A real hassle, even though I loved the final fully 3D scenery it made.
I wanted to do something easy, however. Something that wasn't messy. Had no real cleaning up to do. And so forth. And was light and thin and could easily throw in a drawer for storage. So I turned back to papercraft again. On RPGNOW I came across the Omega Prime Core paper scenery set. It's floors, walls, doors, computers, crates, etc. Not a lot of variation, but some good stuff - and cheap at about $6.
I printed stuff out draft, at low resolution grey scale, then I laminated all the pages, and am now cutting them out and gluing them together. It's a neat system. It has tabs that you stick around the edges of each floor tile, letting them slot together with adjacent floor tiles so they don't slide about. The walls have flaps at the bottom that jut out - and what I've done, is glued long, thin 15mm miniatures bases along the bottom of the walls. The metal strip weighs down the walls, and holds them firmly in place, while allowing me to just pick them up and shift them around to lay out a different map!