SEXTANTE by Victor Olaya is a powerful plugin that bundles many methods and applications from QGIS in one place and provides a GUI for your processing work flow which is comparable with the ArcGIS ModelBuilder or the ERDAS Spatial Modeler.
With this plugin it is very easy to use your GRASS, SAGA and GDAL tools, self-written R scripts and many more.
This makes spatial analysis much easier and increases reproducibility. Especially the combination with R functions provides a completely new dimension of working with a GIS as nearly everything spatially can be converted to a data.frame and be consumed by R then… parallel processing included. Analysing Big (spatial) Data is therefore a little bit easier.
You can find some interesting examples on Victor’s blog or on the QGIS Manual Page.
The tricky part for me was the installation as it was given me an error about some missing dependencies on my system. The SEXTANTE plugin needs an Python module called PSYCOPG2. But there was a simple article on EHOW which describe how to install it on your Ubuntu System. If you are running Windows you can stick to a post on initd.
Previous Posts in this series
QGIS Plugin – Profile Tool
QGIS Plugin – RasterCalc
QGIS Plugin – OpenLayers