Outlined here are several useful sites for georeferenced data that can be used in GIS software.
WorldClim – Global Climate Data
Free GIS Data – a list of free GIS data sources
STATSilk – free shapefile maps
Soil Data through the European Soil Data Centre (ESDAC)
Soil Data through the Food and Agriculture Organization (FAO) Soils Portal of the United Nations
Free GIS Software: