OpenJump is a Java Based, Cross-Platform open source GIS analysis and query tool. We've been using it a lot lately, and I would
say out of all the open source tools (and even compared to many commercial tools) for geospatial analysis, it is one of the best out there.
While it is fairly rich in functionality in terms of doing statistical analysis on ESRI shapefile as well as PostGIS and other formats and also has numerous geometry manipulation features and plugins in its tool belt,
we like the ad-hoc query ability the most. The ease and simplicity of that one tool makes it stand out from the pack. People not comfortable with SQL may not appreciate that feature as much as we do though.
In this excerpt we will quickly go thru the history of project and the ties between the PostGIS group and OpenJump group,
how to install, setup a connection to a PostGIS enabled PostgreSQL database and doing some ad-hoc queries.
GEOS which is a core foundation of PostGIS functionality and numerous other projects, is a C++ port of JTS. New Enhancements often are created in JTS and ported to GEOS and a large body of GEOS work has been incubated
by Refractions Research, the PostGIS incubation company.