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!
Terragen - Terragen is a scenery generator, created with the goal of generating photorealistic landscape...
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
EarthSculptor - EarthSculptor is a realtime terrain height-map editor and paint program featuring an easy to use...
Vue - Create vast expanses of terrains, add trees, select the best point of view and render...
Picogen - The homepage of the free (as in freedom), GPL-licensed Terrain Synthesizer and Renderer named 'picogen'