Triangle Draw - Create awesome graphics.
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!
Isometric - Create beautiful, abstract works of art & optical illusions
Vue - Create vast expanses of terrains, add trees, select the best point of view and render...
Grid Paint - Online grid-based paint program offering squared, triangular, and hexagonal grids.
Picogen - The homepage of the free (as in freedom), GPL-licensed Terrain Synthesizer and Renderer named 'picogen'