THe building(s) on the right are cardstock. All four are attached together so you only ever get 2 walls for each building. They are from The Virtual Armchair General's Mean Streets line. I mounted mine on black foamcore and recessed most of the windows and doors (or removed the doors entirely to build my own). I also added additional details of my own like the wood trim around some of the doors and the skylight and roof building. I also built it so that the top comes off and models can move inside.
The building on the left is the Plasticville firehouse. I cut and glued on a brick pattern to turn it into a warehouse. The I added the wood trim around the bay doors.