DIVA GIS is a free geographic information system (GIS) software package for geo-spatial data analysis. Which is specially designated for biodiversity mapping and habitat suitability modelling etc.
DIVA-GIS Software Interface
DIVA-GIS is also known to provide a lot of free GIS datasets to the user community for mapping and analysis requirements. Users can download GIS data country wise. These are the main datasets: administrative boundaries, roads, railway, altitude, land use/ land cover, population density etc.