L3DT for generating terrain

L3DT is a Windows application for generating terrain maps and textures. It is intended to help game developers and digital artists create large high-quality 3D worlds.

What does it do?
Generating and editing heightmaps
Generating textures, light maps, bump maps, etc.
Calculations and optimisations
File formats: Image formats, including BMP, PNG, TGA, DDS, PGM, PBM, PCX and RAW. Mesh files, including OBJ, X, B3D, 3DS
http://www.bundysoft.com/L3DT/