I picked this up at a dollar tree store after looking thru the kid section.
118770072_3876951635654524_8294288963753387353_o by
matt swain, on Flickr
I would not use it as a straightedge for cutting foamcore or anythihng, but some of the shapes in it might make useful window patterns. The small squares could be used for basic windows in plebe apartments, the larger pentagonal ones could be for cathedrals or similar windows. If you could cut it smoother the half circle might make a good large window especially if you extend the bottom a bit.
So yeah, you can find useful stuff for modeling and terrain damn near anywhere.