Our policy is to promote resources which are free and, to the best of our knowledge, reliable. So we emphasize, but do not necessarily rely exclusively, on open source software and data available freely on the internet.
The WaterBase tools
MapWindow is our current choice of GIS tool.
SWAT (Soil and Water Assessment Tool) is the hydrological modeling tool we are currently using.
FreeGIS is a major source of information on free resources for GIS: tools, geo-data, documentation, and projects