GRASS (the Geographic Resources Analysis Support System) is a software raster- and vector-based GIS (Geographic Information System), image processing system, graphics production system, and spatial modeling system. It contains many modules for raster data manipulation, vector data manipulation, rendering images on the monitor or paper, multispectral image geocoding and processing, point data management and general data management. It also has tools for interfacing with digitizers, scanners, and the PostgreSQL, DBF, and ODBC connected databases. GRASS operates on all common operating systems.
SaVi is satellite visualization software that lets you create, run, examine, and modify satellite orbits in two and three dimensions. Simulations of Iridium, Globalstar, Galileo, GPS, and other satellite constellations are included. SaVi requires Tcl and Tk on a system with Unix libraries. SaVi works well with the 3D renderer Geomview. Geomview is optional, though recommended for its 3D rendering capabilities.
UDIG (User-friendly Desktop Internet GIS) is a spatial data viewer and editor with emphasis on the OpenGIS standards for Internet GIS, the Web Map Server and Web Feature Server standards. It provides a common platform for building spatial applications with open source components.
gvSIG is an easy to use Java desktop GIS. It has a friendly interface, and can access some popular formats (e.g. SHP, DGN, DXF, DWG, TIFF, JPEG, ECW, SID, etc). It will integrate in a single view both local vector and raster data, as well as remote data through WMS or WCS. It allows layout design for printing. It is meant for end-users of geographical information, and currently has Spanish, Valencian, English, and 6 more interfaces. It's designed to be easily extended.
MapMemo allows you to drag your files onto any graphic (map, photo, scan, illustration, screenshot, etc.), and thus give them a visual, location-based relation. It uses only aliases of your files which, when you click on an appropriate location, will open in their original application. You can use layers, info windows, colors, and comment fields to organize your files on the map.
SAGA GIS (System for Automated Geo-scientific Analysis) is a geographical information system (GIS). The SAGA GIS API supports grid data like digital terrain models and satellite images, vector data, and tables. This API makes it easy to implement new algorithms and exempts the developer from hassle programming overhead like user-interface design or file I/O. SAGA GIS comes with a large collection of modules, in areas of terrain-analysis, geo-statistics, image processing, and process simulation.