Quantum GIS (often abbreviated to QGIS) is a free software desktop Geographic Information Systems (GIS) application that provides data viewing, editing, and analysis capabilities.

infiniti Consulting CC. - a small business set up with the goal of helping people to learn and use open source GIS software. “Introducing GIS” is a project sponsored by the Chief Directorate: Spatial Planning & Information, Department of Land Affairs, Eastern Cape, South Africa (DLA) which offers free tutorials on Quantum GIS which is an open source and free GIS software.

KOSMO is one of the most popular open source desktop GIS (Java-based), providing a nice Graphic User Interface (GUI), GIS data editing tools, and spatial analysis functions

gvSIG was developed by the European GIS community offering multiple language user interfaces. More than ten different languages (including Spanish, French and Chinese) can be selected to display the menus and tools. This feature is extremely useful to teach GIS in a non-6 English-spoken community. gvSIG has nice vector data editing functions. Users can easily digitize lines by snapping vertices to existing nodes and generate correct topology. With an easy-to-configure locator map, gvSIG immediately reveals where you are in your dataset.

uDig is also a popular Java-based desktop GIS software. The name, uDig, stands for “User-friendly Desktop Internet GIS”. Therefore, uDig offers strong capabilities to integrate Web mapping technologies, such as WMS, WFS, remote ArcSDE, WCS, GeoRSS and KML. The uDig website includes great tutorials and walkthrough documents for first-time users. uDig is built upon IBM's Eclipse platform with a “clean” user interface. uDig provides several good GIS functions, including the Styled Layer Descriptor (SLD) support, Web Catalog Server support, and thematic mapping with advanced symbology. uDig is also a great choice for Desktop GIS software.

The Integrated Land and Water Information System (ILWIS) is a PC-based GIS & Remote Sensing software, developed by ITC up to its last release (version 3.3) in 2005. ILWIS comprises a complete package of image processing, spatial analysis and digital mapping. It is easy to learn and use; it has full on-line help, extensive tutorials for direct use in courses and 25 case studies of various disciplines. As per July 1st, 2007, ILWIS software is freely available ('as-is' and free of charge) as open source software (binaries and source code) under the 52°North initiative (GPL license). This software version is called ILWIS 3.4 Open.

The Key Indicator Data System (KIDS) has been developed by the World Agriculture Information Centre (WAICENT) of the Food and Agriculture Organization of the United Nations. KIDS is a open-source software framework that provides the ability to implement thematic information systems that collect, reference, visualize, exchange and disseminate statistical, survey and indicator data. Visualization is possible through tables, mapping, raster images and graphs. Basic GIS overlay and legend editing functions are available for non-GIS users.

MapCruncher – a prototype technology from Microsoft Research makes it easy for users to create their own, personalized mash-ups – may. The system revolutionizes the way people use online maps. MapCruncher makes it easy to publish maps overlaid on Virtual Earth. Once you get familiar with the tool, it will take you about ten minutes to make a new map.

GeoNetwork OpenSource is a web based Geographic Metadata Catalogue System developed by FAO-UN, WFP-UN and UNEP. The system implements the ISO19115 Geographic Metadata and ISO 23950 (Z39.50) standards. Furthermore it provides an OGC-WMS client application InterMap OpenSource and integrates the Deegree OGC Web Map Server in its full installer version, including sample data.

Map Maker is simple to use yet powerful map making and GIS software for Windows. It is available as the free program "Map Maker Gratis" and the more advanced "Map Maker Pro". Map Maker Pro is a low-cost system now in use in over 100 countries. It is used in a wide range of environmental work including forestry and fisheries. It supports, raster, vector, and DTM data and can import and export a wide range of formats including ArcView shape files and MapInfo mif/mid files. Map Maker Pro includes 3D features including perspective views, contouring, cross-sections etc.

DIVA-GIS is free geographic information system (GIS) software. DIVA-GIS was specifically developed for use with biological distribution data such as available from natural history museums and genebanks. With DIVA-GIS you can: (i) map the locations of sites where populations of plant or animal species were observed, and of different characters that may have been recorded for these populations. (ii) make grid maps of the distribution of biological diversity, and identify “hotspots” and areas that have complementary levels of diversity; and (iii) extract climate data for localities points, and predict the presence of species based on climate.

GRASS GIS Commonly referred to as GRASS, 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.

The unofficial ARC/INFO AND ARCVIEW symbol page contains useful symbols (markers and lines) and  fill sets.

SPRING, an object-oriented GIS freely available on the Internet. Description: SPRING is a state-of-the-art GIS and remote sensing image processing system with an object-oriented data model which provides for the integration of raster and vector data representations in a single environment.

The World Language Mapping System (WLMS), offers a set of worldwide language homeland areas (polygons) and point locations for use in Geographic Information Systems (GIS). Dataset developed jointly by SIL and GMI maps all languages of the 14th Edition Ethnologue, and includes substantially all of the data of the published Ethnologue as a GIS attribute table.

TUNEP's GRID-Arendal's Online GIS and Map and Graphics Database offers a free collection of maps, graphics and diagrams, illustrating environmental issues. These images are produced using desktop publication software such as Freehand, Adobe Illustrator, CorelDraw , etc.

MapCruzin is dedicated to providing the data, tools, knowledge, and expertise that will help tribes, governments, community groups, and businesses communicate the various facets of environmental, health and social problems, solutions, and achievements in such a way that they educate, raise community awareness, and facilitate networking. Free downloads.

The goal of VTP is to foster the creation of tools for easily constructing any part of the real world in interactive, 3D digital form. This goal will require a synergetic convergence of the fields of CAD, GIS, visual simulation, surveying and remote sensing. VTP gathers information and tracks progress in areas such as procedural scene construction, feature extraction, and rendering algorithms. VTP writes and supports a set of software tools, including an interactive runtime environment (VTP Enviro). The tools and their source code are freely shared to help accelerate the adoption and development of the necessary technologies. To learn more about VTP and the field of virtual terrain, use the subject headings below. You can also request the VTP distribution as a CDROM or download.

AGIS for Windows: A simple mapping and GIS shareware
package

Community Map Builder "The Community Map Builder will provide an Open Source framework which will allow communities to jointly build geographic databases and share them over the web. It will be particulary useful where geographic knowledge is spread across a large group of people." [ License: GNU General Public License (GPL) ]

OpensourceGIS offers a Global index of Open Source / Free GIS related software