FlightGear Flight Simulator: free open-source multiplatform flight sim
A collection of packages providing extra functionality for GNU Octave
Computer Algebra System written in Common Lisp
Library to control radio transceivers and receivers
XFLR5 is an analysis tool for airfoils, wings and planes
An open source software-defined GNSS receiver
Simulate chemical processes using advanced thermodynamic models
Model Railway CAD program
GPS log file viewer and analyzer
A circuit simulator with graphical user interface (GUI)
Scanning probe microscopy data visualisation and analysis
Open source finite element software for multiphysical problems
Cross-platform DICOM implementation
a parametric 3D CAD modeler
Data Analysis, Simulations and Visualization on the Sphere
General Mission Analysis Tool
For exploring cellular automata like Conway's Game of Life.