Jeremy makes 3D Printable “strongholds” based on different themes. So far, a borderlands version and elf version.
28mm Modular Buildings Is our latest Kickstarter, Providing you with Modern, Western, Steampunk & Wasteland Modular Buildings Using the OpenLOCK Connecting system for 3d printing. Hayland also makes a bunch of different tiles and scatter terrain as well as Gaslands Car parts. It covers pretty much all genres.
Terrain 4 Print has a wide selection of scatter terrain for both science fiction and fantasy.
Thunder Chrome has a number of buildings available for your post apocalyptic or Sci-Fi setting.
Modern 3D Models (at this time) that feature walls, vehicles, and other terrain features for a modern wargame.
Maker of 3D Printable Terrain and Miniatures. He has models from WWII to Sci-Fi.