Implementation of Spatial Data Infrastructures (SDIs) for local governments and companies is a task that has gained ample attention in recent years. Different categories of spatial software such as desktop GIS, server GIS, web map servers, spatial database management systems, web map development toolkits, etc., are required to realize the software components of an SDI.
This is an overview of free and open source projects that develop and maintain GIS software that fit within these categories.