For exploring cellular automata like Conway's Game of Life.
Entrain your brain!
Python implementation of the Dual N-Back mental exercise
Emgu CV is a cross platform .Net wrapper for OpenCV
Capture and control API for IIDC compliant cameras
Cross platform (lin/win/mac) geographical information system (GIS)
TI graphing calculators <-> computer communication software
Toolkit for working with and mapping geospatial data
Open source Health IT for the planet
Cross platform GUI for Maxima
fast C++ library for linear algebra & scientific computing
Modbus TCP, UDP and Modbus RTU client/server library