Ricci
- A Mathematica package for doing tensor calculations in differential geometry and general relativity.
- http://www.math.washington.edu/~lee/Ricci/

The Cactus Code
- A modular manageable high-performance 3D tool for Numerical Relativity.
- http://www.cactuscode.org/

Whisky
- A code to evolve the equations of hydrodynamics in curved spacetime (relativistic numerical hydrodynamics).
- http://www.whiskycode.org/

Riemann Package for Maple
- Package written in Maple for calculating tensor components in General Relativity and performing some abstract tensor manipulation; suitable for calculations in general relativity and for quantum field theory in curved spacetime. Features brief description
- http://www.cbpf.br/%7Eportugal/Riemann.html

Riegeom Package for Maple
- Package for the mathematical software Maple: abstract tensor manipulation and component calculation in Riemannian spaces; suitable for a variety of calculations in general relativity. Features a short description, examples, downloads for Maple V, and a li
- http://www.astro.queensu.ca/%7Eportugal/Riegeom.html

openGR
- An open framework for large numerical simulations in general relativity.
- http://wwwrel.ph.utexas.edu/openGR/

LORENE (Langage Objet pour la RElativite NumeriquE)
- Provides a set of C++ classes to solve various problems arising in numerical relativity and other areas of computational astrophysics.
- http://www.lorene.obspm.fr/

GRTensorM
- A version of GRTensor II for use with the Mathematica software.
- http://www.astro.queensu.ca/~grtensor/grtmma.html

GRTensorII
- A computer algebra package for performing differential geometry calculations. Site includes demonstrations of the package's applications to general relativity.
- http://grtensor.org/

GRAVLENS
- Software for modelling gravitational lens systems; created and maintained by Chuck Keeton at Rutgers University.
- http://redfive.rutgers.edu/~keeton/gravlens/

Form Symbolic Manipulation System
- A free software package for manipulating tensors (abstract index notation) and other multi-component objects; highly suitable for calculations in general relativity and related theories such as supergravity. Site includes documentation, course material, a
- http://www.nikhef.nl/~form/

Cartan: A Mathematica Package for Tensor Analysis
- Product information from Ad Infinitum AS about a package for use with the Mathematica software; allows interactive tensor calculations in spacetimes of arbitrary dimension.
- http://adinfinitum.no/cartan/

CarpetCode
- A mesh refinement driver for the Cactus code; the primary application is the simulation of black hole spacetimes.
- http://www.carpetcode.org/