52°North Initiative for Geospatial Open Source Software GmbH is an international research and development company whose mission is to promote the conception, development and application of free open source geo-software for research, education, training and practical use.
AtlasStyler is a user-friendly application to style geodata. The resulting styles can be saved to XML files that follow the OGC SLD/SE standard 1.0.
AVPython - By embedding Python within ArcView GIS, we can break through most of the barriers to interoperability, scalability, and extensibility that the Avenue developer faces when trying to build a modern application. Unlike Avenue, Python is a real programming language suitable for large-scale collaborative development, yet like Avenue it is easy to use, and very easy to read.
FlightGear is an open-source, multi-platform, cooperative flight simulator development project. Source code for the entire project is available and licensed under the GNU General Public License. This is not GIS software but may be of interest to some. Atlas creates free charts of the world for FlightGear.
Geopublisher Software allows you to quickly create digital multimedia atlases and publish them. Visit the demo atlases page to take a look at some publically available atlases or check out the features list to get an impression about the possibilities.
Hope these prove useful. If you are new to GIS, check out the Learn2Map GIS Tutorial and Atlas. We have more free GIS software available and there is plenty of free data and shapefiles that will work with these programs. More to come!