ODE is a high performance library for simulating rigid body dynamics. It is fully featured, stable, mature, and platform independent with an easy-to-use C/C++ API. It has advanced joint types and integrated collision detection with friction. ODE is useful for simulating vehicles, objects in virtual reality environments, and virtual creatures. It is currently used in many computer games, 3D authoring tools, and simulation tools.
Meep is a free finite-difference time-domain (FDTD) simulation software package to model electromagnetic systems. It supports distributed-memory parallel simulations, nonlinear, anisotropic, and dispersive media, PML absorbing boundaries, and 1D/2D/3D and cylindrical problems. It is completely scriptable from either C++ or a Scheme (GNU Guile) interface.
openEMS is an electromagnetic field solver using the FDTD method. It employs a fully 3D Cartesian and cylindrical coordinate graded mesh. Matlab (or Octave) is used as an easy and flexible scripting interface. Advanced Features include: multi-threading, SIMD (SSE), and MPI support for high speed FDTD.
Finesse is a numeric simulation for laser interferometers using the frequency domain and Hermite-Gauss modes. It is easy to use for students. For basic use, including graphical output, no commercial software is required. The implemented physics are well documented in a 180-page manual. Simple examples are provided. Finesse can be used to compute a great variety of interferometer signals for control systems, including longitudinal control, alignment control, and thermal compensation.