OpenJUMP is an open source Geographic Information System (GIS) written in the Java programming language. It is developed and maintained by a group of volunteers from around the globe. OpenJUMP started as JUMP GIS designed by Vivid Solutions.
The current version can read and write shapefiles and simple GML files. It has limited support for the display of images and good support for showing data retrieved from WFS and WMS web-services. So you can use it as GIS Data Viewer. However, it's particular strength is the editing of geometry and attribute data. One can style the appearance of data in OpenJUMP's map display and can export the view to SVG. A growing number of vector analysis tools for topologic analysis and overlay operations is available too. OpenJUMP 1.4 release adds new raster data processing capabilities, and still improve usability with EZ-buttons (to create shortcuts), inverse selection, user-defined selection appearance and a lot of bug fixes. OpenJUMP has limits in reading very large data files and has limited support for cartographic projections. More info in our fatcs sheet.
Detailed information on OpenJUMP can be found on our Wiki.