The "best" depends on what you plan on doing with the software. For landscapes use terragen. Well rounded 3d programs like blender are good. 3D Graphics Blender - http://www.blender3d.org/ Terragen - http://www.planetside.co.uk/terragen/ For more free software and links view my thread http://www.gamerenders.com/forum/index.php?showtopic=159462