FeatureServer is an implementation of a RESTful Geographic Feature Service. (What is REST?) Using standard HTTP methods, you can fetch a representation of a feature or a collection of features, add new data to the service, or delete data from the service.
GRASS GIS (Geographic Resources Analysis Support System) is an open source, free software (FOSS) Geographical Information System (GIS) with raster, topological vector, image processing, and visualization functionality
GDAL is a translator library for raster geospatial data formats that is released under an X/MIT style Open Source license. It also comes with a variety of useful commandline utilities for data translation and processing.