The following list is by no means exhaustive but does identify some of the major open source solutions available in the computational engineering domain.

A Complete Package

CAE Linux is a LiveDVD Linux distribution dedicated to computer aided engineering based around softwares Salomé, Code_Aster, Code_Saturne and OpenFOAM.

General Numerical Analysis

Scilab is a platform for numerical computations similar in capability to MATLAB.

Octave is also a platform for numerical computations with a command line language that is equivalent to MATLAB.

SciPy is a software library for mathematics, science, and engineering with a very large community and its own conference.

CAD and Geometry Tools

BRL-CAD is a powerful cross-platform open source solid modeling system that includes interactive geometry editing, high-performance ray-tracing for rendering and geometric analysis, image and signal-processing tools, a system performance analysis benchmark suite, libraries for robust geometric representation, with more than 20 years of active development.

SALOME is a generic platform for Pre and Post-Processing for numerical simulation.

Open CASCADE Technology is a software development platform that includes components for 3D surface and solid modeling, visualization, data exchange and rapid application development.

FEA Codes

FETK is a collection of adaptive FE software libraries and tools for solving coupled systems of nonlinear geometric partial differential equations. The FETK libraries and tools are written in an object-oriented form of ANSI-C and in C++.

Code_Aster is a FE solver capable of linear and non-linear analysis for statics and dynamics, fatigue, damage, fracture, contact, geomaterials, porous media and multi-physics coupling. English summary document.

CFD Codes

OpenFOAM is a CFD toolbox that can simulate a range of problems including complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics, electromagnetics and the pricing of financial options.

CFD Online provides online center CFD resources.

Mesh Generation

Gmsh is an automatic 3D finite element grid generator with a built-in CAD engine and post-processor.

NETGEN is an automatic 3D tetrahedral mesh generator that is capable of working with constructive solid geometry (CSG) or boundary representation (BRep) geometry.

Visualization Tools

ParaView is a multi-platform application designed to visualize data sets of any size.

MayaVi2 is a general purpose visualization engine.