Useful terrain/texture software

Terragen, by Planetside Software.

World-Machine, by Stephen Schmitt.

PnP Terrain Creator, by Team PnP.

Mega 3D Terrain Generator, by Nem.

Wilbur, by Joe Slayton.

ScapeMaker, by Matthias Buchetics, Dirk Plate, et. al.

Leveller, by Daylon Graphics.

GeoControl, by Cajomi Johannes Rosenberg.

Grome, by Quad Software.

Terragen, by Planetside Software.

VTP Enviro, by the Virtual Terrain Project.

3DEM, by Visualization Software LLC.

Bryce, by DAZ Productions.

Global Mapper, by Global Mapper Software, LLC.

T2, by Toymaker.

Texture Studio, by John Judnich.

ER Mapper — works with tiled mosaics!

VTBuilder, by the Virtual Terrain Project.

3DEM, by Visualization Software LLC.

Global Mapper, by Global Mapper Software, LLC.

A comprehensive list via www.3dlinks.com.

Another good list via the Virtual Terrain Project.