Terragen - Terragen is a scenery generator, created with the goal of generating photorealistic landscape...
Sweet Home 3D - Sweet Home 3D is a free interior design application that helps to draw the plan of house, arrange furniture on it and visit the results in 3D.
World Machine - Command powerful tools like erosion and advanced colormaps to create terrain heightmaps, meshes, and textures for your game or 3D scene. Download for Free!
SketchUp - 3D for Everyone
PnP TerrainCreator - PnP TerrainCreator is a highly integrated tool for large scale terrain creation.
MagicPlan - The floor plan creation app magicplan lets you create dimensioned floor plans without actively measuring or drawing. With its Augmented Reality.