Hydrosheds (USGS - WWF)  http://hydrosheds.cr.usgs.gov/

MrSid data from NASA

SRTM DEM data from NASA (Seamless USGS site containing other data too...)

University of Maryland GLCF - Global Land Cover Facility (lots of imagery...)

SRTM (void-filled seamless data) http://srtm.csi.cgiar.org

Landcare Research: http://www.landcareresearch.co.nz/

National Institute of Water and Atmospheric Research (NIWA): http://www.niwa.co.nz

National Soil Erosion Research Laboratory (NSERL), West Lafayette, Indiana, U.S.A. - http://topsoil.nserl.purdue.edu

U.S. Forest service - www.fs.fed.us

U.S.AID - www.usaid.gov

Peace Corps - www.peacecorps.gov

Environmental Protection Agency - www.epa.org

National Resource Conservation Service (NRCS) - water and climate center - www.wcc.nrcs.usda.gov/hydro/

USDA-ARS Everglades Agro-Hydrology Research Unit (EAHRU)  http://www.ars-grin.gov/ars/SoAtlantic/Miami/Pages/Hydrology/Hydrology.htm

Itaipu Binacional, Foz do Iguaçu, Brazil - www.itaipu.gov.br

Instituto Agronomico do Parana, Brazil - www.iapar.br

United Nations Environmental Program - www.unep.org

United Nation Development Program - www.undp.org

World Bank - www.worldbank.org

New Zealand Hydrological Society:  http://hydrologynz.org.nz

ASAE - the Society for engineering in agricultural, food, and biological systems: www.asae.org

Soil and Water Conservation Society - www.swcs.org/

International Soil Conservation Organization: http://www.isco.org/

GIS links (geographic information systems): http://www.gisuser.co.nz/

Care International - www.care.org

Rainforest Action Network - www.ran.org

The Nature Conservancy - www.tnc.org or www.nature.org

Conservation International - www.conservation.org

World Wildlife Fund - www.wwf.org

Earth Watch - www.earchwatch.org

The Earth Council - www.ecouncil.ac.cr

Fundacion Amigos de la Naturaleza (FAN-Bolivia) - www.fan-bo.org

Museo Knoel Kemp Mercado de Historia Natural - www.museonoelkempff.org

Centro Internacional de Agricultura Tropical (CIAT) - www.ciat.cgiar.org

Chemonics International Inc. - www.chemonics.com

Food and Agriculture Organization (F.A.O.) - www.fao.org

Center for International Forest Research (CIFOR) - www.cgiar.org/cifor/

International Center for Research in Agroforestry (ICRAF) - www.icraf.cgiar.org

International Society of Tropical Foresters (ISTF) - www.cof.orst.edu/org/isft

International Union for the Conservation of Nature (IUCN) - www.iucn.org