Open Source software is gaining ground in the GIS software business. The scientific community is coming together to use, create, and enhance open source GIS tools. The development of open source GIS is usually driven by very active communities closely collaborating with different university-level institutions and thus oriented to concrete solutions, e.g. in environmental science or modelling and on technological improvements. Besides that, most open source software is available for free and the users can benefit from the availability and transparency of the open source (program) code, which may be adapted for specific consumer needs and can again be shared within the community. Furthermore, open source software becomes more and more platform-independent and integrative between various projects, libraries, and standards. Some of the software that exists for open source GIS includes the System for Automated Geoscientific Analysis (SAGA, http://www.saga-gis.org), the Geographic Resources Analysis Support System (GRASS, http://grass.osgeo.org), and Quantum GIS (QGIS, http://www.qgis.org/). QGIS is based on an intuitive mapping interface with optional plugins (supplementary program code providing additional functionalities, similar to ESRI ArcGIS extensions) for geoprocessing, analysis, and interoperability with various other software, standards, and data types. GRASS is more advanced in terms of its inherent spatial analytical ability especially for raster data, but some programming knowledge is of advantage for more sophisticated analysis and script automation. The integration of GRASS applications in QGIS through a plugin has a long tradition in the QGIS history, meaning that one can benefit from the strengths of both systems at once. Furthermore, the latest releases of QGIS provide a toolbox called “SEXTANTE” (http://www.sextantegis.com) where various Open Source software and libraries like SAGA can be accessed through the straightforward user interface of QGIS. Chapter 7 provides a tutorial for QGIS with basic applications adapted to honey bee research. For further information about open source GIS software and the different projects mentioned above see the Open Source Geospatial Foundation website http://www.osgeo.org.