ArcGIS is a system that lets you easily author data, maps, globes, and models on the desktop and serve them out for use on a desktop, in a browser, or in the field via mobile devices, depending on the needs of your organization. Server GIS gives you the ability to create, manage, and distribute GIS services over the Web to support desktop, mobile and Web mapping applications.
this is a Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization. GRASS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies.
For additional information, please refer to: GRASS: LSU Overview.
Quantum GIS is an open source GIS (Geographic Information System) application that runs on Mac, Windows, and Linux. It’s sort of a professional grade version of Google Earth, allowing you to work with detailed maps in raster, vector, or database format. It also opens files in the format produced by Arc GIS.