Cactus is a general, modular, parallel environment for solving systems of partial differential equations. The code has been developed over many years by a large international collaboration of numerical relativity and computational science research groups and can be used to provide a portable platform for solving any system of partial differential equations.
EGO is a program to perform molecular dynamics simulations on parallel as well as on sequential computers. Supported parallel machines include the Hitachi SR8000, CRAY-T3E, IBM-SP2, Fujitsu VPP700, Parsytec-CC under PARIX, and inhomogeneous clusters of UNIX workstations under PVM or MPI. EGO also runs sequentially on any decent UNIX workstation, even Windows95/NT PC's (with a GNU-C compiler) can be used.
Ghemical is a molecular modelling software package with some nice 3D visualization tools. It supports methods based on both molecular mechanics and quantum mechanics (using MOPAC7, and MPQC for QM). The geometry optimization (for MM and QM) and molecular dynamics (for MM) algorithms are included. Ghemical is written in C++, and hopefully offers a good framework for a generic freeware molecular modelling tool.
Viewmol is a program for building and editing molecules as well as for the visualization of outputs from quantum chemical and molecular mechanics programs. Currently supported are Gaussian 9x, Gamess, Discover, DMol/DSolid/DMol3, Gulp, Mopac, Turbomole, and PDB files. Properties visualized include geometry (with various drawing modes), vibration (animated or with arrows), optimization history/MD trajectories, MO energy level diagram, MOs, basis functions, and electron density. Drawings can be saved as TIFF, HPGL, Postscript, and input files for Rayshade. Viewmol has an embedded Python interpreter for automation. The program is language independent and currently "speaks" English, French, German, Russian, or Spanish.
VMD (Visual Molecular Dynamics) is designed for the visualization and analysis of biological systems such as proteins, nucleic acids, lipid bilayer assemblies, etc. It may be used to view more general molecules, as VMD can read standard Protein Data Bank (PDB) files and display the contained structure. VMD provides a wide variety of methods for rendering and coloring a molecule: simple points and lines, CPK spheres and cylinders, licorice bonds, backbone tubes and ribbons, cartoon drawings, and others. VMD can be used to animate and analyze the trajectory of a molecular dynamics (MD) simulation. In particular, VMD can act as a graphical front end for an external MD program by displaying and animating a molecule undergoing simulation on a remote computer. VMD uses OpenGL and OpenGL Programmable Shading Language for high performance rendering of large structures.