Cross platform (lin/win/mac) geographical information system (GIS)
Blender addons to make the bridge between Blender and geographic data
Interactive, thoroughly customizable maps in the browser
Viking is a free/open source program to manage GPS data
GPS track editor for editing tracks and planning (multiple) day tours
Plugins for OpenCPN
A small nifty program where you build you own ZOO
FastVersion is a Qgis plugin for data versioning in a Postgis database
OpenSeaMap Depth Contours
Toolbox for geoscientists and geo enthusiasts
Source code for ArcGIS Viewer for Flex - a great application framework
Open Street Map (OSM) tools, OSM/XML parser, tag extractor
Customization of OpenGTS look and feel
Interactive OpenGL map projection and navigation with geodetic utils.