Esri’s ArcGIS is the reference in desktop GIS mapping software. But unless you’re able to dish out $1,500 for the basic license, you’re pretty much out of luck. Or are you? QuantumGIS may not be as powerful or comprehensive as Esri’s, but shares just as many of the basic functions and tools. It’s free, and as an open-source software, anyone can contribute to improve what QGIS gets to offer.
But let’s not forget that GIS relies profoundly upon database management. The quality of geospatial data is only as strong as the quality of its database.
Boston GIS: PostGIS/PostgreSQL tutorial