Using OpenMap, you can quickly build applications and applets that access data from legacy databases and applications. OpenMap provides the means to allow users to see and manipulate geospatial information. This JavaBean-based toolkit includes many of the standard desktop GIS features, including visualization and editing.

Quantum GIS (QGIS) is a Geographic Information System that runs on Linux, Unix, Mac OS X, and Windows. QGIS supports vector, raster, and database formats.It can access PostGIS databases, in addition to dozens of other vector and raster formats. It supports feature labeling and has a great user community. Extensibility is provided through a plugin environment.

This popular internet mapping application has both programming interfaces and a web CGI mode. Programming interfaces exist for several languages. It also includes command-line tools for creating static image files of maps, legends, scale bars, and so on.

The JUMP Unified Mapping Platform (JUMP) is a GUI-based application for viewing and processing spatial data. It includes many functions common to other popular GIS products for the analysis and manipulation of geospatial data.This feature-rich desktop GIS environment can create, edit, and manipulate data. It can do much more through additional plugins. JUMP is a Java application and has several levels of programming interfaces available.

OpenEV is a library, and reference application for viewing and analyzing raster and vector geospatial data.If you want to do a quick digitizing job, OpenEV can get you up and running easily. It doesn't have a lot of fancy editing tools, but reads in dozens of raster and vector data types, which you can then use as a base for drawing your own shapes. It has a Python scripting environment and includes many image enhancement tools.

PostGIS is a PostgreSQL database that can also store geometric (spatial) data types, it is an excellent way to bring tabular and spatial data together into a common management environment. PostGIS has the ability to manipulate data as well as store it. This provides GIS-like abilities within an SQL database environment. The SQL functions include buffer, intersection, within, distance, and more. These functions take geometric data from columns in PostGIS tables and return new geometries or other information.