GRASS GIS: Mighty Free GIS
FWTools: Open Source GIS Binary Kit
PostgreSQL / PostGIS: Free database and the spatial database extension PostGIS
Virtual Terrain Project: Software for 3D Visualisation and a great source for information about terrain visualisation.
There are already extensive Link Lists in the Net:
FOSSGIS -> Software/ Logiciels
Geo Community - Links to Free GIS Software and propritary GIS Software
